Testing And Adjusting

Usage:

Introduction

Reference: See 768C Tractor & 769C Truck Power Train, SENR6868, for Systems Operation.

Reference: See 768C Tractor & 769C Truck Power Train, SENR6867, for Specifications. If the Specifications in SENR6867 are not the same as in the Systems Operation and the Testing And Adjusting, look at the printing date on the front cover of each book. Use the Specifications given in the book with the latest date.

Specifications

Torque Converters

Outlet Relief Valve

Torque converter outlet pressure at stall speed ... 410 ± 70 kPa (60 ± 10 psi)

Inlet Relief Valve

Torque converter inlet pressure ... 930 ± 35 kPa (135 ± 5 psi)

Secondary And Parking Brake Valve

Parking brake release pressure at high idle setting ... 3170 ± 200 kPa (460 ± 30 psi)

Lockup Clutch And Synchronizing Valve Group

Pressure Reduction Valve

Lockup clutch pilot pressure at high idle setting ... 1725 ± 100 kPa (250 ± 15 psi)

Modulation Reduction Valve

Lockup clutch maximum pressure at low idle setting ... 1515 ± 105 kPa (220 ± 15 psi)

Lockup clutch primary pressure at low idle setting ... 1100 ± 35 kPa (160 ± 5 psi)

Transmission

Transmission Hydraulic Control Group

Pressure Control Valve Group

Selector And Pressure Control Valve Group

Transmission Pump Pressure Relief Valve

Maximum pump pressure (at high idle) ... 3210 kPa (465 psi)

Minimum pump pressure (at low idle) ... 2690 kPa (390 psi)

Priority Reduction Valve

Pilot pressure ... 1725 ± 70 kPa (250 ± 10 psi)

Transmission Lubrication Pressure

Transmission lubrication pressure at high idle setting ... 165 to 235 kPa (24 to 34 psi)

Transmission lubrication pressure at low idle setting ... 4 kPa (.5 psi) minimum

Brief Summary of Operation

Power Train System Basic Diagram (Simplified)

1. The transmission speed sender measures (senses) ground speed.

2. The transmission control determines when to shift by the signal from the transmission speed sender. The transmission control activates the solenoids to make the shifts.

3. The body raise switch is used in the test mode (condition). The body raise switch also prevents reverse operation of the transmission during raise and lower operation of the body.

4. The secondary/parking brake switch and service/retarder brake switch are inputs to the transmission control. When the secondary/parking or service/retarder brake switches are activated, the anti-hunt timer is deactivated. The service/retarder switch, when activated, will make the shift speeds higher.

5. The transmission speed distributor lets the same output from the transmission speed sender by used for the speedometer and AETA (Automatic Electronic Traction Aid).

6. When an upshift or downshift solenoid is activated, it send pressure oil to the rotary actuator, which turns the rotary selector spool. This sequence causes a different pair (two) of clutches to be engaged for the next speed.

7. Transmission hydraulic controls individually (separately) control the time to engage (fill time) and disengage (release time) each clutch and the maximum pressure in each clutch.

8. When the lockup solenoid is activated, pressure oil is sent to the modulation reduction valve of the lockup clutch valve. This engages the lockup clutch of the torque converter for direct drive.

9. The shift lever switch selects desired speed and direction.

10. The transmission switch tell the transmission control to stop shifting and reminds the control what gear the transmission is in. The transmission switch is turned by the rotary selector spool.

General Description

Power Train Systems Basic Diagram (Simplified)

The power train is made up of four basic systems.

1. Transmission Control (Electrical System).

2. Torque Converter.

3. Transfer Gears and Transmission.

4. Differential and Final Drives.

These four basic systems connect to each other either electrically, hydraulically or mechanically. A basic diagram shows what components are common to each system.

Components Of The Power Train
(1) Differential and bevel gear. (2) Pinion. (3) Transmission. (4) Transfer gears. (5) Front drive shaft. (6) Torque converter. (7) Final drives and axles. (8) Wheels and tires. (9) Rear drive shaft. (10) Lockup clutch. (11) Engine.

Manual Shift Procedure

During troubleshooting it is sometimes necessary to shift the transmission. This is done by turning the rotary selector spool when the engine is off.

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NOTICE

To prevent possible damage to the flexible coupling, never manually shift the transmission by rotating the flexible coupling for the transmission switch.

1. Remove the plug from the transmission case.

2. Install a 9S-1721 Extension 25 (1/4) inch square drive] 101.6 mm (4.00 in) long in the end of the rotary selector spool. Install a 9S-1723 Reversible Ratchet on the extension.

3. Move the ratchet clockwise (toward the rear of the machine) until the rotary selector spool will not turn any more. This is NEUTRAL position.

4. From NEUTRAL position, turn the ratchet counterclockwise (toward the front of the machine) through all detent positions of the rotary selector spool. The positions from NEUTRAL and REVERSE, FIRST, SECOND, THIRD, FOURTH, FIFTH, SIXTH and SEVENTH speeds respectively.

NOTE: There is approximately 30° of rotation between each detent of the rotary selector spool.

Ratchet And Extension Installed In The Rotary Selector Spool

Shift Inhibiting

A shift from any speed into NEUTRAL is not inhibited (prevented). The transmission can always be shifted to NEUTRAL.

If the ground speed of the machine is less than 5 km/h (3 mph) in any forward speed and the transmission shift lever is moved to REVERSE, the transmission will immediately shift to REVERSE. If the ground speed is more than 5 km/h (3 mph) in any forward speed and the transmission shift lever is moved to REVERSE, the transmission will immediately make a shift to NEUTRAL. The transmission will then shift to REVERSE, when the ground speed decreases to less than 5 km/h (3 mph).

Adjustment For Hoist Control Linkage

The hoist control linkage must be correctly adjusted when the machine is equipped with a transmission neutralizer.

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The transmission on this machine will neutralize when the transmission shift lever is in REVERSE and the hydraulic control lever is in either RAISE or Lower position. The neutralizer will not stop the vehicle from rolling. Use the brakes to stop. Make reference to WARNING on the first page of HYDRAULIC SYSTEM TESTING AND ADJUSTING section.

If the truck has a transmission neutralizer and the transmission does not go from REVERSE to NEUTRAL when the control lever (1) is moved to either the RAISE or LOWER position, a linkage adjustment may be necessary. An electric failure in the neutralizer switch or wires could also be the cause.

Hydraulic Control Lever
(1) Control lever. (2) 287 ± 5 mm (11.3 ± .2 in) dimension. Lever in the FLOAT position, dimension to the top of cab floor plate without floor mat.

Control lever (1) (located to the left of the operator's seat) must be 287 ± 5 mm (11.3 ± .2 in) from the top of the cab floor without the floor mat to the bottom of the handle when the lever is in the FLOAT position. If the measurement for dimension (2) is not correct, the control linkage needs an adjustment.

Control Linkage Adjustment

Control Linkage Rods
(3) Rod from the shaft for the control lever in the cab. (4) Rod to the lever on the hydraulic control in the hydraulic oil tank. (5) Fitting on the end of the rod.

Loosen the locknuts on rod (3) that is against fitting (5) and disconnect the fitting from the lever. If the measurement for dimension (2) is too much, turn fitting (5) in the direction to make rod (3) longer. Make the length of rod (3) shorter if measurement (2) is not enough.

The length for rod (3) is approximately 1195 mm (47.0 in). The length of rod (4) is 1185.0 mm (46.65 in).

Neutralizer Switch Adjustment (Body Raise Switch)

Neutralizer Switch
(6) Bolt (hidden). (7) Bracket. (8) Switch and plate. (9) Yoke.

It may be necessary to adjust the location of the neutralizer switch if the linkage dimensions are correct. Remove the cover from the back of the operator's cab and then remove the four bolts which hold the switch cover (box) to the inside wall of the cab. Remove the cover (box) from over the switch in the cab.

Move control lever (1) to the FLOAT position. The lower roller on yoke (9) must be near but not against the short lever (not shown in the illustration) between the two rollers on the yoke.

If it is necessary to change the position of the yoke, move the control lever to the FLOAT position. Loosen bolt (6) and then move switch and plate (8) until the lower roller on yoke (9) is near but not against the short lever. Tighten the bolt.

If the position of yoke (9) cannot be correctly adjusted by moving switch and plate (8) on bracket (7), it will be necessary to make either one of the next two adjustments.

One of the adjustments is to make the length of rod (3) either longer or shorter until the lower roller on yoke (9) is very near the short lever when control lever (1) is in FLOAT position.

NOTE: When rod (3) is made longer, be sure control lever (1) can be easily moved to the LOWER position.

The second adjustment is for the location of yoke (9) on the switch. Put the control lever in the FLOAT position and loosen the setscrew in the yoke. Move the yoke so that the lower roller, on the yoke, is near but is not against the short lever between the rollers on the yoke. Tighten the setscrew in the yoke.

Troubleshooting The Power Train

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Sudden movement of the machine can cause injury to persons on or near the machine. To prevent possible injury, do the procedure that follows before troubleshooting the power train.

1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. Put the transmission shift lever in NEUTRAL position. Engage the parking and secondary brakes. Stop the engine.

2. Permit only two people in the cab (one operator and a service person). The machine operator must only operate the machine as told by the service person. The service person will look at all lights (LED's) or gauges. Keep all other personnel either away from the machine or in view of the operator.

3. Make sure the transmission rotary selector spool is in NEUTRAL position.

For locations of components and electrical connectors, see the Electrical Schematic, SENR5652. For hydraulic components or pressure tap locations see the Torque Converter and Transmission Hydraulic Troubleshooting sections in this module.

Visual Checks are the first steps when troubleshooting a problem. The visual checks will find the problems that can be more quickly corrected. If the visual checks do not shown any problems, the Operational Checks are the next steps to follow. The operational checks will permit the identification of possible problems with the machine during operation.

Visual Checks

Perform visual checks first when troubleshooting a problem. Make the checks with the engine stopped. Place the shift lever in NEUTRAL and the transmission rotary selector spool in Neutral. Engage the parking brake.

Check A

Inspect the oil levels in the transmission and hydraulic oil tank.

NOTE: Many problems in the power train are caused by low oil level or air in the oil. If the engine has not been started and run for several minutes, this oil level check will make sure there is oil in the transmission and the engine can be started. If the machine has sat overnight or longer without the engine running, the oil level will be high. An accurate oil level check can be made after the oil is hot.

Check B

Inspect all oil lines, hoses and connections for damage or leaks. Look for oil on the ground under the machine.

NOTE: If oil can leak out of a fitting or connection, air can leak in. Air in the system can be as bad as not enough oil.

Check C

Inspect the transmission control fuse, harnesses and electrical connectors (refer to the Electrical Schematic).

With the key switch and disconnect switch OFF, check the 10 ampere fuse for the transmission. If the fuse is open (broken or missing filament) replace it.

Inspect the electrical harnesses for damaged or broken wires. Disconnect each connector and look for bent, broken or pulled out (removed) pins and sockets. Also look for any foreign material inside the connectors. The connectors must be tightened with normal force. They must also disconnect with the same amount of force.

Check D

Check the batteries. Turn the disconnect switch ON. Listen for the supplemental steering motor to run for around 30 seconds. If the supplemental steering motor fails to run, inspect the starting and charging system before Visual Check E.

Check E

Inspect transmission oil filter, magnetic screen and suction, parking brake release oil filter and torque converter oil filter.

NOTE: Parking brake release oil filter, transmission oil filter and torque converter oil filter each have an oil filter bypass valve. An oil filter bypass valve lets oil bypass (go around) the oil filter element(s) whenever the pressure difference between inlet oil and outlet oil at the oil filter gets too high. Any oil that does not go through the filter element(s) goes directly into the hydraulic circuit. Dirty oil causes restrictions in valve orifices, sticking valves, etc.

The pressure setting of the bypass valves in the parking brake release oil filter, the torque converter oil filter, and the transmission oil filter is approximately 250 kPa (36 psi).

If any contamination is found in the filter elements or screens all components of the transmission (power train) hydraulic system must be cleaned. Do not use any damaged parts. Any damaged parts must be removed and new parts installed.

Check F

Check transmission control (electrical system). See SENR5665 for procedures.

Operational Checks

The operational checks that follow are designed to educate (train) the service personnel in a correct troubleshooting procedure and method. The checks and procedures are set in a sequence to find most problem(s) and/or probable cause(s) quickly. These operational checks must be done in order, starting with Check 1. Do not go to the next check until either the problem in the previous check has been corrected, or instructed to do so. If the correct result for the check is found, as instructed in the procedure, go directly to the next check or procedure.

Take note of all WARNINGS and NOTICES in these checks. Never start the next check until you read and understand the warnings or notices.

The checks that follow can be used to find many of the problems that will be found during the operation of the machine. These checks will also give an indication of the system in which the problems can be found.

Machine Preparation For Checks

1. Engage the parking brakes. Be sure the shift lever is in NEUTRAL and the transmission rotary selector spool is in NEUTRAL position.

2. Check all fluid levels on the machine (engine oil, engine coolant, hydraulic oil, differential, transmission, etc.). Make sure the torque converter oil is SAE 10W oil, transmission oil is SAE 30 oil and that No. 2 diesel fuel is used for the engine fuel.

NOTE: The oil levels can be above the FULL mark at this time. With the engine running, both transmission and torque converter oil must be at the normal temperature for operation.

3. The engine must be STOPPED. Do not start the engine until told differently.

4. The tachometer must be at zero rpm.

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Some of the checks that follow must be done with the machine in operation. A trained machine operator will be needed. Whenever the engine is in operation, the machine operator must be in the cab with the parking and service brakes ENGAGED until told differently.

Lockup Clutch And Solenoid Valve Check

Check 1.

This check determines if:

The electrical signal gets to the lockup solenoid.

The lockup solenoid electrically activates.

Procedure:

1. Do not start the engine.

2. Disconnect the cab harness plug from the transmission control and disconnect the harness connector for the lockup solenoid. Put a jumper wire from Socket 1 to Socket 5 of the cab harness plug (for the transmission control). This will supply + 24 volts through the machine harness to actuate the lockup solenoid.

3. Touch the lockup solenoid chassis harness connector to the lockup solenoid.

4. Each time the connector touches the solenoid a "click" and/or "buzz" must be felt and/or heard.

Problem 1:

The "click" and/or "buzz" is not felt or heard.

Probable Cause:

a. Bad lockup solenoid.

b. Broken (open or grounded) wire or harness to the lockup solenoid.

Check 2:

This check determines if:

The lockup clutch pressure are correct.

Procedure:

1. Disconnect the upshift solenoid and downshift solenoid harness connectors.

2. The transmission shift lever must be in NEUTRAL and the transmission rotary selector spool must be in the NEUTRAL position. The jumper wire must still be connected from Socket 1 to Socket 5 of the transmission control harness connector plug.

3. Connect a 4000 kPa (600 psi) pressure gauge to the pressure tap for the lockup clutch.

Pressure Gauge Tap Location For Lockup Clutch

4. Start and run the engine at LOW IDLE. Touch the lockup solenoid chassis harness connector to the solenoid. Each time the connector touches the solenoid, the pressure on the gauge must read 1520 ± 105 kPa (220 ± 15 psi).

Problem 1:

The pressure on the gauge is 0 kPa (0 psi) at all times.

Probable Cause:

See Troubleshooting The Torque Converter Hydraulic System. Do Lockup Clutch Checks.

Problem 2:

The pressure on the gauge is not 0 kPa (0 psi) when the lockup solenoid is not activated.

Probable Cause:

See Troubleshooting The Torque Converter Hydraulic System. Do Lockup Clutch Checks.

Problem 3:

The pressure on the gauge is not correct when the solenoid is activated.

Probable Cause:

See Troubleshooting The Torque Converter Hydraulic System. Do Lockup Clutch Checks.

Transmission and Transmission Control Check

Check 3.

This check determines if:

The transmission switch operates and is installed (timed) correctly.

The transmission clutches engage.

The transmission control operates.

Procedure:

1. Disconnect all electrical harness connectors from the upshift, downshift and lockup solenoids. Start and run the engine at LOW IDLE.

2. Engage the parking brakes and service brakes. The front brake on-off valve on the instrument panel must be ON.

3. Do the shift sequence that follows for REVERSE and each FORWARD speed (FIRST, SECOND, THIRD, FOURTH FIFTH, SIXTH and SEVENTH).

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NOTICE

Check the brake oil temperature gauge regularly. Do not let the brake (torque converter and hoist hydraulic) oil temperature get too hot during this shift sequence. This can cause damage to the brakes, torque converter and hoist hydraulic system. The "T.C./Retarder Oil Temperature" indicator on the electronic monitoring panel (EMS), and the action lamp will flash when the temperature is too hot to operate in this condition. When the brake (torque converter) oil temperature gets too hot, put the transmission in NEUTRAL and run the engine at approximately 1500 rpm until the temperature returns to the normal operating range.

Shift Sequence:

a. Manually rotate the transmission rotary selector spool to the desired speed. After the manual shift is made, move away from the machine.

b. Gradually increase engine rpm to approximately 1300 rpm or until the machine starts to pull through the brakes, whichever happens first.

c. Look at the rear end of the drive shaft. When there is correct transmission clutch operation, only a small amount of rotation (less than one complete turn) will be seen, except in NEUTRAL. If the machine starts to pull through the brakes before 1300 rpm, there is no need to look at the drive shaft.

d. Decrease the engine rpm to LOW IDLE. Shift to the next speed position. Do Steps a, b, and c of the shift sequence again. This will help in the identification of a slipping (partially engaged) clutch. Continue this sequence for the remainder of the speeds until SEVENTH speed is made.

Problem 1:

The machine starts to creep (move) forward before engine rpm gets to 1300 rpm.

Probable Cause:

Brake System. See Air System And Brakes, SENR6882.

Problem 2:

The drive shaft does NOT turn in NEUTRAL.

Probable Cause:

See Troubleshooting The Torque Converter Hydraulic System. Do Visual Checks.

Problem 3:

When a shift is made to REVERSE or any FORWARD speed, the engine stops running.

Probable Cause:

See Troubleshooting The Torque Converter Hydraulic System. Do Visual Checks.

Problem 4:

The drive shaft turns in one or more speeds other than NEUTRAL, but the wheels do not turn. (Clutch or clutches not engaging in transmission.)

Probable Cause:

See Troubleshooting The Transmission Hydraulic System. Do Visual Checks.

Problem 5:

The transmission will not stay in the manually shifted (selected) speed position. Manual shifts are hard in any direction (upshift or downshift).

Probable Cause:

Solenoid Leakage:

- shifts to higher speed from the selected shift (bad upshift solenoid).

- shifts to lower speed from the selected shift (bad downshift solenoid).

Torque Converter Hydraulic System Troubleshooting

The troubleshooting for the torque converter hydraulic system is divided into four sections: torque converter, lockup clutch, hoist and brake cooling. The reason for this division is to save time and make it easier to find the correct troubleshooting information.

Make reference to the following warning and pressure tap locations for all checks and tests. If the problem area (torque converter, lockup clutch, hoist or brake cooling) is not known, do the checks and tests in the order they are given. For all tests, the oil must be at normal temperature of operation.

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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, do the procedure that follows before testing and adjusting the torque converter.

1. Move the machine to a smooth horizontal location. Move away from working machines and personnel.

2. Put the transmission shift lever in NEUTRAL position. Stop the engine.

3. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.

4. Engage the parking brakes.

Pins Installed In Body Of Truck

5. Fully raise the body and install the two pins at the rear of the truck.

Hoist Control Linkage

6. Disconnect the hoist control linkage as shown. Remove the cotter pin and pin that connects the rod to the hoist control lever.

7. Make sure the transmission rotary selector spool is in NEUTRAL position.

8. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.

Test Equipment

If 1U-5481 Pressure Gauge Group and 1U-5482 Pressure Adapter Group are not available, the tools that follow are needed.

Transmission Clutch and Torque Converter Information

Hydraulic Schematics

Torque Converter Hydraulic System In Direct Drive, (Lockup Clutch Engaged), Engine Running

(1) Lockup solenoid.

(2) Selector piston for lockup clutch.

(3) Load piston for lockup clutch.

(4) Pressure reduction valve.

(5) Lockup clutch and solenoid valve group.

(6) Modulation reduction valve for lockup clutch.

(7) Outlet relief valve for torque converter.

(8) Secondary and parking brake valve.

(9) Relief valve for brake release system.

(10) Passage to rear wheel brakes.

(11) Inlet relief valve for torque converter.

(12) Torque converter.

(13) Oil cooler for torque converter and brakes.

(14) Oil pump drive.

(15) Parking brake release oil filter.

(16) Torque converter oil filter.

(17) Lockup clutch for the torque converter.

(18) Screen.

(19) Parking brake release section of oil pump.

(20) Torque converter charging section of oil pump.

(21) Torque converter scavenge section of oil pump.

(22) Scavenge screen.

(23) Left rear wheel brake.

(24) Right rear wheel brake.

(25) Hydraulic oil tank.

(26) Oil pump for hoist hydraulics and rear brake cooling.

(27) Suction screen.

(28) Oil cooler relief valve for rear brakes.

(29) Control valve for hoist hydraulics.

(30) Return oil screen for hoist hydraulics.

(31) Suction screen.

(A) Pressure tap for pilot oil.

(B, H) Pressure taps for parking brake release oil.

(D) Pressure tap for torque converter outlet.

(E) Pressure tap for brake cooling (cooler outlet).

(F) Pressure tap for brake cooling (cooler inlet).

(G) Pressure tap for torque converter inlet.

(J) Pressure tap for brake cooling (inlet).

(K) Pressure tap for brake cooling (outlet).

(L) Pressure tap for brake cooling (inlet).

(M) Pressure tap for brake cooling (outlet).

Location Of Components And Pressure Taps

Torque Converter Lines Top View
(8) Secondary and parking brake valve. (12) Torque converter. (13) Oil cooler for torque converter and brakes. (16) Torque converter oil filter. (25) Hydraulic oil tank.

Section A-A
(5) Lockup clutch and solenoid valve group. (7) Outlet relief valve for torque converter. (11) Inlet relief valve for torque converter. (14) Oil pump drive. (19) Parking brake release section of oil pump. (20) Torque converter charging section of oil pump. (21) Torque converter scavenge section of oil pump. (A) Pressure tap for pilot oil. (B) Pressure taps for parking brake release oil. (C) Pressure tap for torque converter lockup clutch. (D) Pressure tap for torque converter outlet. (G) Pressure tap for torque converter inlet.

Right Side, Behind Front Wheel
(15) Parking brake release oil filter. (H) Pressure taps for parking brake release oil.

Right Side Of Engine
(E) Pressure taps for brake cooling (cooler outlet). (F) Pressure taps for brake cooling (cooler inlet).

Front Of Right Rear Wheel Brake
(J) Pressure taps for brake cooling (inlet). (K) Pressure taps for brake cooling (outlet).

Front Of Left Rear Wheel Brake
(L) Pressure taps for brake cooling (inlet). (M) Pressure taps for brake cooling (outlet).

Troubleshooting The Hydraulic System When The Oil Gets Too Hot (Overheating Conditions)

Instrument Panel
(1) Brake oil temperature gauge. (2) T.C./retarder oil temperature alert indicator.

An overheating problem in the hydraulic system will probably be seen first through the warning system. brake oil temperature gauge (1) and T.C./Retarder oil temperature alert indicator (2) both sense (feel) the temperature of torque converter outlet oil.

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NOTICE

Check the brake oil temperature gauge regularly. Do not let the brake (torque converter and hoist oil temperature get too hot during this shift sequence. This can cause damage to the brakes, torque converter, and hoist hydraulic system. The T.C./Retarder oil temperature alert indicator on the electronic monitoring panel (EMS), and the action lamp will flash when the temperature is too hot to operate in this condition. When the brake (torque converter) oil temperature gets too hot, put the transmission in NEUTRAL and run the engine at approximately 1500 rpm until the temperature returns to the normal operating range.

Brake Oil Temperature Gauge (1)

Problem 1:

The brake oil temperature gauge gives the indication that oil temperature is too hot. The T.C./Retarder oil temperature indicator is OFF.

Probable Cause:

Electrical system. See:

Schematic 768C Tractor and 769C Truck Electrical System, SENR6839.

Problem 2:

The brake oil temperature gauge gives the indication that oil temperature is not too hot. The T.C./Retarder oil temperature indicator is ON.

NOTE: The T.C./Retarder oil temperature indicator activates (comes ON) at approximately 124°C (255°F). The indicator stays activated (remains ON) until the oil temperature decreases to approximately 110°C (230°F). Therefore, it is possible for the brake oil temperature gauge to indicate that oil temperature is not too hot while the T.C./Retarder temperature indicator is activated (ON).

Probable Cause:

Electrical system. See electrical schematic.

Problem 3:

The brake oil temperature gauge gives the indication that oil temperature is too hot. The T.C./Retarder oil temperature indicator is ON.

Probable Cause:

Improper operation of the machine.

Reference: See the Operation & Maintenance Manual, SEBU6747 for 768C Tractor and 769C Truck for correct operating techniques of the brake system.

Machine not operated correctly. Operate the machine again. Make sure that engine rpm does not get below 1700 rpm. This will make sure enough oil goes through the torque converter and brake oil coolers to keep the oil at normal operating temperature.

Problem 4:

The conditions in Problem 3 are still the same after the machine is operated again.

Probable Cause:

A restriction in brake cooling system:

a. To easily see if there is a restriction in the system, remove the cover from the makeup oil tank for the brake hydraulic system.

Example Of Oil Flow At Low Idle rpm

b. Start and run the engine at LOW IDLE rpm in NEUTRAL. There must be a constant flow of oil (as shown) from the inlet tube into the makeup oil tank.

c. Increase engine rpm to HIGH IDLE. The flow of oil must increase as shown.

Example Of Oil Flow At High Idle rpm

If flow is not as shown for LOW IDLE and HIGH IDLE, the cause could be:

1. Failure of the hoist and rear brake cooling oil pump (3), parking brake release oil pump (4), torque converter charging oil pump (5). Do Visual Checks For The Hydraulic System in this manual.

NOTE: For flow and pressure checks, reference Form SENR5645, 771C & 775B Quarry Truck Air System and Brakes, Troubleshooting The Brake Cooling System.

Location Of Hoist And Rear Brake Cooling Oil Pump (3)

Location Of Parking Brake Release Oil Pump (4) And Torque Converter Charging Oil Pump (5)

2. The rear brake oil cooler relief valve pressure is set to low. Bench test oil cooler relief valve (6) to see if it is adjusted correctly.

Location Of Rear Brake Oil Cooler Relief Valve (6)

3. Restriction in the hose assembly from hydraulic tank to makeup oil tank.

Visual Checks For The Hydraulic System (Includes Torque Converter, Brake Cooling and Hoist Hydraulic Systems)

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Make reference to the WARNING on the first page of Troubleshooting The Torque Converter Hydraulic System.

Do Visual Checks first when troubleshooting a problem. Make the checks with the engine STOPPED and the parking brakes ENGAGED. Put the transmission shift lever in NEUTRAL and the transmission rotary selector spool in NEUTRAL. During these checks, use a magnet to separate ferrous particles from non-ferrous particles (O-ring seals, aluminum, bronze, etc.).

The following checks make up the visual checks part of the troubleshooting section:

Check 1. Oil level in hydraulic oil tank.

Check 2. Leakage.

Check 3. Parking brake release oil filter.

Check 4. Torque converter oil filter.

Check 5. Torque converter scavenge screen.

Check 6. Oil cooler screens.

Check 7. Parts inside hydraulic oil tank.

Check 8. Inspect return oil screen.

Check 1:

Check the oil level in the hydraulic oil tank. Look for air or water in the oil (at the sight gauge). Many problems in the hydraulic system are caused by low oil level or air in the oil. Add oil to the hydraulic tank if it is needed. The torque converter, brake cooling and hoist hydraulic systems use SAE 10W oil.

Inner Right Side Of Main Frame
(1) Torque converter oil filter.

Outer Right Side Of Main Frame
(2) Parking brake release oil filter.

NOTE: Parking brake release oil filter (2) and torque converter oil filter (1) each have an oil filter bypass valve. An oil filter bypass valve lets oil bypass (go around) the oil filter element(s) whenever the pressure difference between inlet oil and outlet oil at the oil filter gets too high. Any oil that does not go through the filter element(s) goes directly into the hydraulic circuit. Dirty oil causes restrictions in valve orifices, sticking valves, etc.

The pressure setting of the bypass valves in parking brake release oil filter (2) and in torque converter oil filter (1) is approximately 250 kPa (36 psi).

Problem 1:

The oil level is too high.

Probable Cause:

Worn or damaged engine crankshaft rear seal lets engine oil into the torque converter cover.

Problem 2:

There is an indication of water in the oil.

Probable Cause:

Failure of oil cooler (3) for the hoist pump oil, torque converter oil to rear brakes.

Oil Cooler (3)
(Viewed from engine compartment)

Problem 3:

There is an indication of air in the oil.

Probable Cause:

Do Visual Check 2.

Problem 4:

The oil level is too low.

Probable Cause:

a. Do Visual Check 2. Add oil before any tests are done.

b. Check the oil level in each final drive. Brake cooling oil can leak into the final drive.

Final Drive Plug

Check 2:

Inspect all oil lines, hoses and connections for damage or leaks. Look for oil on the ground under the machine.

NOTE: If oil can leak out of a fitting or connection, air can leak in. Air in the system can be as bad as not enough oil.

Check 3:

Remove and inspect (cut apart if necessary) parking brake release oil filter (2) for foreign material.

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Shiny steel particles are found.

Probable Cause:

Mechanical failure of parking brake release section (4) of the oil pump.

Three Section Pump
(4) Parking brake release pump section. (5) Torque converter charging pump section. (6) Torque converter scavenge pump section. (7) Torque converter cover. (8) Scavenge screen (inside cover).

Check 4:

Remove and inspect (cut apart if necessary) torque converter oil filter (1) for foreign material.

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Shiny steel particles are found.

Probable Cause:

Mechanical failure of torque converter charging pump section (5).

Check 5:

Drain cover (housing) (7) of the torque converter. Measure the amount of oil removed from the cover. Inspect scavenge screen (8) for foreign material and/or a restriction.

Problem 1:

More than 19 liters (5 U.S. gal) of oil are drained from the cover.

Probable Cause:

Restriction in scavenge screen (8).

Problem 2:

More than 19 liters (5 U.S. gal) of oil are drained from the cover and aluminum particles are found.

Probable Cause:

Mechanical failure of the torque converter.

Problem 3:

More than 19 liters (5 U.S. gal) of oil are drained from the cover. During Visual Check 7, shiny steel particles were found in bottom of the hydraulic tank.

Probable Cause:

Mechanical failure of torque converter scavenge pump section (6).

Problem 4:

Iron or steel chips are found.

Probable Cause:

a. Worn flywheel or starting motor gear on engine. Inspect the starting motor and flywheel gears.

b. Worn drive or driven gear on torque converter charging pump section (5).

c. Mechanical failure of oil pump drive (9). Drain and inspect the oil pump drive.

Inside Left Frame
(9) Oil pump drive. (10) Hoist hydraulics and rear brake cooling oil pump.

Problem 5:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 6:

Bronze particles are found.

Probable Cause:

Worn lockup clutch in the torque converter.

Check 6.

Remove and inspect screen (11) for foreign materials.

Right Side Of Engine
(11) Screen (between elbows).

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

A large quantity of aluminum particles are found in screen (11).

NOTE: A small amount of aluminum particles from (wear of) hoist hydraulics and rear brake cooling oil pump (10) is normal.

Probable Cause:

Mechanical failure of hoist hydraulics and rear brake cooling oil pumo (10). Do Visual Check 8.

Problem 3:

Shiny steel and/or chrome particles are found in screen (11).

Probable Cause:

Mechanical failure of a hydraulic cylinder and/or rod (look at cylinder rods for scoring, etc.).

Problem 4:

Aluminum particles are found in screen (12).

Probable Cause:

Mechanical failure of the torque converter.

Check 7:

Drain the oil from the hydraulic oil tank. Remove outer cover of the tank. Inspect oil removed from and the inside of the tank for foreign materials. Also remove, inspect and clean suction screens (12) and (13).

Hydraulic Oil Tank
(12) Suction screen for torque converter charging and parking brake release oil. (13) Suction screen for hoist and rear brake cooling oil. (14) Hoist return oil screen.

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Shiny steel particles are found.

Probable Cause:

Mechanical failure of torque converter scavenge pump section (6).

NOTE: This would result in an excessive amount of oil being drained from the torque converter cover (housing) (7). See Visual Check 5.

Problem 3:

Pieces of red nonferrous material (part of brake disc) are found.

Probable Cause:

Failure of one or more of the wheel brakes.

Check 8:

Remove and inspect hoist return oil screen (14) for foreign material.

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Shiny steel and/or chrome particles are found in return oil screen (14).

Probable Cause:

Mechanical failure of a hydraulic cylinder and/or rod (look at cylinder rods for scoring, etc.).

Problem 3:

Large quantity of aluminum particles are found in return oil screen (14).

NOTE: A small amount of aluminum particles from (wear of) hoist hydraulics and rear brake cooling oil pump (10) is normal.

Probable Cause:

Mechanical failure of hoist hydraulics and rear brake cooling oil pump (10).

NOTE: If any of the above particles are found during any visual check, all components of the torque converter, brake cooling and hoist hydraulic systems must be cleaned. Do not use any damaged parts. Any damaged parts must be removed and new parts installed.

Torque Converter Tests

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Make reference to the WARNING on the first page of Troubleshooting The Torque Converter Hydraulic System.

Test 1. Torque Converter Outlet Pressure

This test will show if:

a. The torque converter operates correctly.

b. Outlet relief valve (1) for the torque converter is set correctly.

Procedure:

1. Install the 9U-7400 Multitach Group on the engine. The 9U-7400 Multitach Group can measure engine rpm by the use of either the photo pickup and reflective tape, or a magnetic pickup or tachometer generator. Special Instruction, NEHS0605 has instructions for its use.

9U-7400 Multitach Group

Outlet Relief Valve (1) For The Torque Converter
(A) Pressure tap for torque converter outlet.

2. At pressure tap (A), connect a hose to the nipple. Connect a pressure gauge [2000 kPa (290 psi)] to the hose.

3. Start and run the engine at LOW IDLE rpm in NEUTRAL.

4. The drive wheels must not turn during a stall test. Make sure that air pressure is at the normal pressure for operation. Put the front brakes on-off valve in the ON position. Engage the parking brakes and the service brakes.

NOTE: If the brakes do not prevent machine movement, put the machine against a solid object that will not move.

5. Make sure that the brake (torque converter) oil is at normal operating temperature. Check to make sure that HIGH IDLE and LOW IDLE rpm are correct according to Fuel Setting And Related Information Fiche.

6. Move the transmission shift lever to REVERSE position.

7. Slowly increase the engine rpm to MAXIMUM GOVERNOR SETTING. The machine will try to move.

8. The engine rpm must be 1980 ± 65 rpm with the torque converter in a stall condition.

9. The pressure on the gauge must be 410 ± 70 kPa (60 ± 10 psi).

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NOTICE

Overheating can cause possible damage to the torque converter, engine and brakes. To avoid overheating do not operate torque converter stall for very long periods of time.

10. When this test is complete, put the transmission shift lever in NEUTRAL and stop the engine. Remove the test equipment.

Problem 1:

High idle rpm is correct (Step 5), but stall speed (rpm in Step 7) is too high. Torque converter outlet pressure is correct.

Probable Cause:

Bad torque converter.

Problem 2:

Torque converter outlet pressure is too low. The oil gets too hot during normal operation.

Probable Cause:

Do Test 2.

Problem 3:

Torque converter outlet pressure is too low.

Probable Cause:

Do Test 2.

Outlet Relief Valve (1) For The Torque Converter
(2) Spacers.

Problem 4:

Torque converter outlet pressure is too high. The oil temperature is not too hot.

Probable Cause:

The setting of the outlet relief valve is too high. Remove spacers (1), see Spacer Chart For Outlet Relief Valve.

Problem 5:

Torque converter outlet pressure is correct. The oil gets too hot during normal operation.

Probable Cause:

See the section, Troubleshooting Torque Converter Hydraulic System When The Oil Gets Too Hot.

Test 2. Torque Converter Inlet Pressure

This test will show if:

a. Inlet relief valve (3) for the torque converter is open.

b. Inlet relief valve (3) is set correctly.

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NOTICE

Inlet pressure to the torque converter MUST NOT be over 930 ± 35 kPa (135 ± 5 psi) with COLD OIL. Higher pressures will damage the torque converter. Adjustment of inlet relief valve (3) must only be done during a bench test.

Inlet Relief Valve (3) For The Torque Converter
(4) Hose assembly to hydraulic tank. (B) Pressure tap for torque converter inlet.

Procedure:

1. Make sure that brake (torque converter) oil is at operating temperature.

2. Disconnect hose assembly (4) from inlet relief valve (3). Block or plug the end of the hose assembly so that oil does not drain out of the hydraulic tank.

3. Install another hose to inlet relief valve (3). Put the other end of this hose in a container (bucket, pan, etc.).

4. At pressure tap (B), remove the plug and install a nipple.

5. With a coupler (and hose if necessary), connect a pressure gauge [2000 kPa (290 psi)] to the nipple.

6. Start and run the engine at LOW IDLE rpm in NEUTRAL. Immediately check the container to see if any oil is in it.

7. If there is any oil in the container, stop the engine. See Problem 1.

NOTE: Connect hose assembly (4) to the inlet relief valve before Step 8 is done.

8. If there is no oil in the container, gradually increase engine rpm to HIGH IDLE in NEUTRAL. The pressure on the gauge must be 930 ± 35 kPa (135 ± 5 psi) at any time.

9. When this test is complete, stop the engine. Remove the test equipment.

Problem 1:

There is oil in the container (coming from the inlet relief valve).

Probable Cause:

a. Spool is stuck open in inlet relief valve (3). Disassemble the valve to correct the problem or install a new valve.

b. Inlet relief valve (3) is set too low. Bench test the valve to see if it is adjusted correctly. The correct pressure setting is 930 kPa (135 psi). Add spacers (5), see Spacer Chart For Inlet Relief Valve.

Problem 2:

There is no oil in the container. Torque converter outlet pressure [at pressure tap (A)] is too low.

Probable Cause:

The setting of outlet relief valve (1) is too low. Add spacers (2), see Spacer Chart For Outlet Relief Valve (Test 1).

Problem 3:

Torque converter inlet pressure is too high.

Probable Cause:

Bench test inlet relief valve (3) to see if it is adjusted correctly. Remove spacers (5), see Spacer Chart For Inlet Relief Valve.

Inlet Relief Valve (3) For Torque Converter
(5) Spacers.

Lockup Clutch Tests

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Make reference to the WARNING on the first page of Troubleshooting The Torque Converter Hydraulic System.

Test 1. Parking Brake Release Pressure

This test will show if:

a. Parking brake release section (1) of oil pump is good.

b. Parking brake relief valve (2) is set correctly.

Location Of Parking Brake Release Section Of Pump (1)

Procedure:

NOTE: Parking brake release pressure can be checked at either pressure tap (A) or (B).

Lockup Clutch And Solenoid Valve Group
(A) Pressure tap for parking brake oil (PMP).

Parking Brake Oil Filter
(B) Pressure tap for parking brake oil (on top of base).

1. Remove the plug at pressure tap (A) or (B). Install a nipple where the plug was removed.

2. With a coupler (and hose if necessary), connect a pressure gauge [15 850 kPa (2300 psi)] to the nipple.

3. With the parking brakes engaged, start and run the engine at HIGH IDLE rpm in NEUTRAL. The pressure on the gauge must be 3170 ± 200 kPa (460 ± 30 psi).

4. When the test is complete, stop the engine and remove the test equipment.

Problem 1:

Oil pressure is low.

Probable Cause:

a. Failure of parking brake release section (1) of oil pump.

b. The setting of relief valve (2) for the parking brake release system is too low. Remove cap (5) and loosen nut (3). Turn threaded rod (4) clockwise to increase pressure. One turn increases the setting approximately 690 kPa (100 psi).

Problem 2:

Oil pressure is too high.

Probable Cause:

The setting of relief valve (2) for the parking brake release system is too high. Remove cap (5) and loosen nut (3). Turn threaded rod (4) counterclockwise to decrease pressure. One turn decreases the setting approximately 690 kPa (100 psi).

Secondary And Parking Brake Valve
(2) Relief valve for parking brake release system. (3) Nut. (4) Threaded rod. (5) Cap.

Test 2. Lockup Clutch Pilot Pressure

This test will show if:

Pressure reduction valve (6) is set correctly.

Procedure:

1. At pressure tap (C), remove the plug and install a nipple.

NOTE: The nipple can be permanently installed at pressure tap (C).

2. With a coupler (and hose if necessary), connect a pressure gauge [3400 kPa (580 psi)] to the nipple.

Lockup Clutch and Solenoid Valve Group
(C) Pressure tap for lockup clutch pilot oil (RV).

3. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The pressure on the gauge must be 1725 ± 100 kPa (250 ± 15 psi).

4. Stop the engine. After the pressure is set correctly, remove the test equipment.

Lockup Clutch And Solenoid Valve Group
(6) Pressure reduction valve. (7) Shims.

Problem 1:

Oil pressure is too low.

Probable Cause:

Add shims (7). See Shim Chart For Pressure Reduction Valve.

Problem 2:

Oil pressure is too high.

Probable Cause:

Remove shims (7). See Shim Chart For Pressure Reduction Valve.

Test 3. Lockup Clutch Leakage

This test will show if:

There are bad seals in the lockup clutch.

Procedure:

Lockup Clutch and Solenoid Valve Group
(D) Pressure tap for torque converter lockup clutch (LU).

1. Remove fitting from pressure tap (D).

2. Start and run the engine at LOW IDLE rpm in NEUTRAL.

3. Measure the amount of oil that comes out of pressure tap (D) in one minute. Install fitting when this check is complete.

Problem 1:

More than 3.8 liter/min (1 U.S. gpm) of oil comes out of pressure tap (D).

Probable Cause:

Bad seals in the lockup clutch.

Test 4. Lockup Clutch Maximum Pressure

This test will show if:

a. Maximum lockup clutch pressure is correct.

b. The operation of the modulation reduction valve is correct.

Procedure:

1. Disconnect the electrical harness connector from the lockup solenoid.

2. Disconnect the cab harness plug from the transmission control. Put a jumper wire from Socket 1 to Socket 5 of the cab harness plug (for the transmission control). This supplies +24 volts to activate the lockup solenoid.

3. At pressure tap (D), use a coupler (and hose if necessary) and connect a pressure gauge [3400 kPa (580 psi)] to the nipple.

4. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The pressure on the gauge must be 0 kPa (0 psi).

5. Look at the pressure gauge and connect the electrical harness to the lockup solenoid. The pressure on the gauge must be 1515 ± 105 kPa (220 ± 15 psi).

6. Remove the electrical harness connector from the lockup solenoid. The pressure on the gauge must go back to 0 kPa (0 psi).

7. Stop the engine. After the problem is corrected, remove the test equipment.

Lockup Clutch And Solenoid Valve Group
(8) Cover. (9) Selector piston plug. (10) Selector piston. (11) Shims. (12) Load piston plug. (13) Load piston orifice. (14) Spring. (15) Spring. (16) Shuttle valve.

Problem 1:

Oil pressure in Step 4 is not 0 kPa (0 psi).

Probable Cause:

a. Selector piston (10) is stuck (will not go back to its original position).

b. Weak or broken spring (15).

c. Lockup solenoid is bad (leaking).

Problem 2:

Oil pressure in Step 5 is 0 kPa (0 psi).

Probable Cause:

a. Little or no pilot oil. Do Test 2.

b. Incorrect operation of chamber shuttle valve (16).

c. Weak or broken spring (14).

Problem 3:

Oil pressure in Step 5 does not increase above 1100 kPa (160 psi).

Probable Cause:

a. Load piston plug (12) is not installed.

b. Load piston orifice (13) is plugged.

c. Selector piston (10) is stuck (will not move).

Problem 4:

Oil pressure in Step 6 decreases slowly or low pressure remains (stays) in the lockup clutch.

Probable Cause:

a. Incorrect operation of shuttle valve (16).

b. Selector piston (10) is stuck (will not move).

Problem 5:

Oil pressure in Step 5 is too low.

Probable Cause:

Do Test 5.

Problem 6:

Oil pressure in Step 5 is too high.

Probable Cause:

Do Test 5.

Test 5. Lockup Clutch Primary Pressure

This test will show if:

Lockup clutch pressure is adjusted correctly.

Procedure:

1. Make sure that the electrical harness connector is connected to lockup solenoid.

2. Make sure the cab harness plug is removed from the transmission control and the jumper wire is installed from Socket 1 to Socket 5 of the cab harness plug.

3. Remove cover (8) from the lockup clutch and solenoid valve group.

4. Remove load piston plug (12) and install cover (8) again.

5. At pressure tap (D), use a coupler (and hose if necessary) and connect a pressure gauge [2000 kPa (290 psi)] to the nipple.

6. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The pressure on the gauge must be 1100 ± 35 kPa (160 ± 5 psi).

7. Stop the engine. After the pressure is set correctly, remove the test equipment.

Problem 1:

Oil pressure is 0 kPa (0 psi).

Probable Cause:

Selector piston plug (9) is not installed.

Problem 2:

Primary pressure is too low.

Probable Cause:

Add shims (11). See Shim Chart For Modulation Reduction Valve.

Problem 2:

Primary pressure is too high.

Probable Cause:

Remove shims (11). See Shim Chart For Modulation Reduction Valve.

Transmission Hydraulic System Troubleshooting

Make reference to the following warning and pressure tap locations for all checks and tests of the transmission hydraulic system. If the problem area is not known, do the checks and tests in the order they are given. For all tests, the oil must be at normal temperature of operation.

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1. Move the machine to a smooth horizontal location. Move away from working machines and personnel.

2. Put the transmission shift lever in NEUTRAL position. Stop the engine.

3. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.

4. Engage the parking brakes.

Pins Installed On Body Of Truck (Typical Example)

5. Fully lift the body and install the two pins at the rear of the truck.

Hoist Control Linkage Disconnected

6. Disconnect the hoist control linkage as shown. Remove the cotter pin and pin that connects the rod to the hoist control lever.

7. Make sure the transmission rotary selector spool is in NEUTRAL position.

8. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.

Test Equipment

A minimum quantity of gauges and fittings needed: ^*

^*To save time on tests, use the quantity of gauges and fittings that follow:

Transmission Speed And Clutch Engagement

Transmission Hydraulic Schematic

Transmission Hydraulic System In FOURTH speed, Engine Running

(1) Charging section of transmission oil pump.

(2) Valve (oil cooler bypass).

(3) Transmission oil filter.

(4) Downshift solenoid.

(5) Upshift solenoid.

(6) Rotary actuator.

(7) Selector piston for No. 3 clutch.

(8) Load piston for No. 3 clutch.

(9) Modulation reduction valve for No. 3 clutch.

(10) Pressure control group.

(11) Modulation reduction valve for No. 5 clutch.

(12) Load piston for No. 5 clutch.

(13) Selector piston for No. 5 clutch.

(14) Transmission oil tank.

(15) Transmission oil cooler.

(16) Scavenge section of transmission oil pump.

(17) Suction screen.

(18) Magnetic screen.

(19) Reservoir in transmission case.

(20) Modulation reduction valve for No. 4 clutch.

(21) Load piston for No. 4 clutch.

(22) Selector piston for No. 4 clutch.

(23) Priority reduction valve.

(24) Neutralizer valve.

(25) Rotary selector spool.

(26) Selector group.

(27) Selector piston for No. 1 clutch.

(28) Load piston for No. 1 clutch.

(29) Modulation reduction valve for No. 1 clutch.

(30) Modulation reduction valve for No. 6 clutch.

(31) Load piston for No. 6 clutch.

(32) Selector piston for No. 6 clutch.

(33) Selector piston for No. 2 clutch.

(34) Load piston for No. 2 clutch.

(35) Modulation reduction valve for No. 2 clutch.

(36) Oil cooler relief valve.

(37) Modulation reduction valve for No. 7 clutch.

(38) Load piston for No. 7 clutch.

(39) Selector piston for No. 7 clutch.

(40) Relief valve.

(41) Passage for transmission lubrication.

(A) Pressure tap for No. 3 clutch.

(B) Pressure tap for No. 1 clutch.

(D) Not used.

(E) Pressure tap for No. 5 clutch.

(F) Pressure tap for No. 4 clutch.

(G) Pressure tap for No. 6 clutch.

(H) Pressure tap for No. 7 clutch.

(J) Pressure tap for upshift pressure.

(K) Pressure tap for downshift pressure.

(L) Pressure tap for pump.

(M) Pressure tap for pilot oil.

(N) Pressure tap for transmission lubrication.

Location Of Components

Transmission Lines And Filter
(1) Charging section of transmission oil pump. (2) Transmission oil cooler bypass valve. (3) Transmission oil filter. (13) Torque converter and brake oil cooler. (14) Transmission oil tank (section). (15) Magnetic screen (inside transfer gear case). (16) Scavenge section of transmission oil pump.

Pressure Tap Locations

(A) Pressure tap for No. 3 clutch. (B) Pressure tap for No. 1 clutch. (C) Pressure tap for No. 2 clutch. (D) Not used. (E) Pressure tap for No. 5 clutch. (F) Pressure tap for No. 4 clutch. (G) Pressure tap for No. 6 clutch. (H) Pressure tap for No. 7 clutch. (M) Pressure tap for pilot oil.

(L) Pressure tap for pump. (M) Pressure tap for pilot oil.

Visual Checks

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Make reference to the WARNING on the first page of Transmission Hydraulic System Troubleshooting.

Do Visual Checks first when troubleshooting a problem. Make the checks with the engine STOPPED and the parking brakes ENGAGED. Put the transmission shift lever and transmission rotary selector spool in NEUTRAL. During these checks, use a magnet to separate ferrous particles from non-ferrous particles (O-ring seals, aluminum, etc.).

Check 1:

Check the oil level in the transmission oil tank. Look for air or water in the oil (through the sight gauge). Many problems in the transmission are caused by low oil level or air in the oil. Add oil to the transmission oil tank if it is needed. The transmission hydraulic system uses SAE 30 oil.

Inner Right Side Of Main Frame
(1) Transmission oil filter.

NOTE: There is an oil filter bypass valve on the inlet side of the transmission oil filter. The oil filter bypass will open and let oil bypass (go around) the oil filter element whenever the pressure difference between inlet oil and outlet oil through the oil filter gets above 250 kPa (36 psi). Any oil that does not go through the filter element goes directly into the hydraulic circuit. Dirty oil will cause restrictions in valve orifices, sticking valves, etc.

Problem 1:

There is an indication of water in the oil.

Probable Cause:

Failure of the transmission oil cooler.

Problem 2:

There is an indication of air in the oil.

Probable Cause:

Do Visual Check 2.

Problem 4:

The oil level is too low.

Probable Cause:

Do Visual Check 2.

Check 2:

Inspect all oil lines, hoses, and connections for damage or leaks. Look for oil on the ground under the machine.

NOTE: If oil can leak out of a fitting or connection, air can leak in. Air in the system can be as bad as not enough oil.

Check 3:

Remove and inspect (cut apart if necessary) transmission oil filter (1) for foreign material.

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Shiny steel particles are found.

Probable Cause:

Mechanical failure of the charging section of transmission oil pump.

Check 4:

Remove and inspect magnetic screen (2) for foreign material.

Bottom Of Transfer Gear Case
(2) Magnetic screen (behind cover).

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Bronze particles are found.

Probable Cause:

Worn clutches in the transmission.

Problem 3:

Iron or steel chips are found.

Probable Cause:

Broken components in transfer gears or transmission.

Problem 4:

Aluminum particles are found.

Probable Cause:

Worn housings, load pistons or selector pistons in the pressure control group.

Check 5:

Remove the plugs in the bottom of the transmission case. This will drain all of the oil out of the transmission and transfer gears. Measure the total amount of oil removed at both plugs. Inspect the oil for foreign material.

Drain Plugs For Transmission Case

Problem 1:

More than 26 liters (7 U.S. gal) of oil is drained from the transmission and transfer gears.

Probable Cause:

a. Restriction in magnetic screen (2).

b. Failure of the scavenge section of the transmission oil pump.

c. Too much leakage in a clutch or clutches of the transmission.

Problem 2:

Rubber particles are found.

Probable Cause:

Seal failure.

Problem 3:

Bronze particles are found.

Probable Cause:

Worn clutches in transmission.

Problem 4:

Iron or steel chips are found.

Probable Cause:

Broken components in transmission or transfer gears.

Check 6:

Drain the oil from the transmission oil tank. Inspect the bottom of the oil tank for debris. Remove and clean suction screen (3).

Hydraulic Oil Tank
(3) Suction screen.

Problem 1:

Rubber particles are found.

Probable Cause:

a. Seal failure.

b. Hose failure.

Problem 2:

Shiny steel particles are found.

Probable Cause:

Mechanical failure of scavenge section of the transmission oil pump.

Problem 3:

Bronze particles are found.

Probable Cause:

Worn clutches in the transmission.

Problem 4:

Aluminum particles are found.

Probable Cause:

Worn housings, load pistons or selector pistons in the pressure control group.

NOTE: If any of the above particles are found during any Visual Check, all components of the transmission hydraulic system must be cleaned. Do not use any damaged parts. Any damaged parts must be removed and new parts installed.

Transmission Hydraulic System Tests

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Make reference to the WARNING on the first page of the Transmission Hydraulic System Troubleshooting.

Test 1. Transmission Pump Pressure

This test will show if:

a. Charging section of the transmission oil pump is good.

b. Relief valve (1) is set correctly.

Procedure:

1. At pressure tap (L), use a coupler (and hose if necessary) and connect a pressure gauge [3400 kPa (580 psi)] to the nipple.

Location Of Pressure Tap (L) For Pump (Pressure), (M) Pressure for Pilot Oil

2. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The minimum pressure on the gauge should be 2690 kPa (390 psi).

3. Run the engine at HIGH IDLE rpm in NEUTRAL. The maximum pressure on the gauge should be 3210 kPa (465 psi).

4. When this test is complete, stop the engine and remove the test equipment.

Selector Group
(1) Relief valve. (2) Spacers.

Problem 1:

Oil pressure is too low.

Probable Cause:

a. Failure of charging section of transmission oil pump.

b. The setting of relief valve (1) is too low. Add spacers (2), see Spacer Chart for Relief Valve. Adjust for LOW IDLE setting.

Problem 2:

Oil pressure is too high.

Probable Cause:

The setting of relief valve (1) is too high. Remove spacers (2), see Spacer Chart for Relief Valve. Adjust for the LOW IDLE setting.

Test 2. Transmission Lubrication Pressure

This test will show if:

a. Oil pressure to the transmission lubrication circuit is good.

b. Transmission lubrication relief valve (3) is closed.

Procedure:

1. At pressure tap (N), use a coupler (and hose if necessary) and connect a pressure gauge [400 kPa (58 psi)] to the nipple.

Location Of Pressure Tap (N) For Transmission Lubrication (Typical Example)

2. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The pressure on the gauge must be a minimum of 4 kPa (.5 psi).

3. Run the engine at HIGH IDLE rpm in NEUTRAL. The pressure on the gauge must be 165 to 235 kPa (24 to 34 psi).

4. When this test is complete, stop the engine and remove the test equipment.

Problem 1:

The transmission pump pressure is correct (Test 1). Transmission lubrication pressure is too low.

Probable Cause:

a. Transmission lubrication relief valve (3) is open.

b. Too much leakage in the transmission lubrication circuit (bad seals, etc.).

Selector Valve
(3) Transmission lubrication relief valve.

Problem 2:

The oil gets too hot during normal operation.

Probable Cause:

Too much oil in transmission case. Do Visual Check 5.

Test 3. Pilot Pressure

This test will show if:

The operation and setting of priority reduction valve (4) is correct.

Procedure:

NOTE: If Tests 4 and/or 5 are to be performed and FT1874 Transmission Test Cover is to be used, perform Steps 1 through 6 and go on to the next test. Pilot pressure can be checked while clutch pressures are checked.

1. Disconnect the wiring harness from the downshift solenoid and upshift solenoid.

2. Remove the solenoid guard and large cover from the transmission case.

3. Remove the plug from pressure tap (M).

4. Install a 3B-6552 Elbow [.125 (1/8 in) NPT] in pressure tap (M). Connect a 3B-7282 Nipple [.125 (1/8 in) NPT X 152 mm (6 in) long] with a 6V-4142 Nipple to the elbow.

5. Put the large cover back on top of the transmission case. To prevent the release (spray) of oil and to keep dirt out, use a piece of plastic or paper along with the cover.

Alternate Step 5. Install the FT1874 Transmission Test Cover in place of large cover. Use four bolts evenly spaced to hold cover in place.

6. Connect a pressure gauge [3400 kPa (580 psi)] to the nipple.

7. Start and run the engine at LOW IDLE rpm in NEUTRAL. Keep the parking brakes engaged.

8. The pressure on the gauge must be 1725 ± 70 kPa (250 ± 10 psi).

9. When the test is complete, stop the engine.

Selector Group
(4) Priority reduction valve. (5) Rotary selector spool. (6) Screen. (7) Spacers. (8) Neutralizer valve. (M) Pressure tap for pilot oil.

Problem 1:

The pressure on the gauge is too low.

Probable Cause:

The setting of priority reduction valve (4) is too low. Add spacers (7), see Spacer Chart for Priority Reduction Valve.

Problem 2:

The pressure on the gauge is too high.

Probable Cause:

The setting of priority reduction valve (4) is too high. Remove spacers (7). See Spacer Chart for Priority Reduction Valve.

Problem 3:

The pressure on the gauge is correct, but the pressures at ALL clutches are 0 kPa (0 psi) (Test 4).

Probable Cause:

a. The operation of neutralizer valve (8) is not correct. Disassemble the selector group. Check for foreign material or worn or damaged parts. Make sure the orifice and/or ball check valve of the neutralizer valve are free of any debris.

b. Restriction in screen (6) in rotary selector spool (5).

Problem 4:

The pressure on the gauge is correct, but the pressures at ALL clutches are too low (Test 4).

Probable Cause:

Restriction in screen (6) in rotary selector spool (5).

Test 4. Pressure Control Group Clutch Pressures

This test will show if:

a. Transmission clutch pressures are correct.

b. There is too much oil leakage in a clutch.

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1. Move the machine to a smooth horizontal location. Move away from working machines and personnel.

2. Put the transmission shift lever in NEUTRAL position. Engage the parking brake. Stop the engine.

3. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.

4. On a truck, raise the body and install the two pins at the rear of the truck.

5. Disconnect the hoist control linkage. Remove the cotter pin and pin that connects the rod to the hoist control lever.

6. Make sure the transmission rotary selector spool is in NEUTRAL position.

7. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.

8. Disconnect the rear drive shaft from the rear of the transmission.

9. Make sure the test cover is installed on the transmission case before any tests are done.

Procedure To Manually Shift The Transmission With The Engine Running (Drive Axles Removed)

This procedure will save time when the transmission is tested. Instead of the use of the transmission shift lever in the operator's station, shifts can be made down on the transmission.

1. Make sure the transmission shift lever is in NEUTRAL position.

2. Disconnect the wiring harness from the downshift solenoid.

Ratchet And Extension Installed In The Rotary Selector Spool

3. With the engine STOPPED, remove the plug (for the rotary selector spool) from the left side of the transmission case.

4. Use the .25 (1/4) inch square drive extension and ratchet to turn the transmission rotary selector spool. When the ratchet is turned clockwise as far as it will go, rotary selector spool (5) is in NEUTRAL position. The order of detent positions from NEUTRAL is REVERSE and FIRST through SEVENTH speeds respectively.

Procedure:

NOTE: If FT1874 Transmission Test Cover is used, a gauge can be installed at pressure tap (M) to check pilot pressure. If 6V-6064 Transmission Test Cover is used, make sure the plug is installed at pressure tap (M).

1. Disconnect the wiring harness from the downshift solenoid and upshift solenoid. Remove the solenoid guard and large cover from the top of the transmission case. Install FT1874 Transmission Test Cover in place of the large cover. Use four bolts to hold the test cover in position.

Alternate Step 1. Remove small cover from large cover and install 6V-6064 Transmission Test Cover in place of the small cover. Use four nuts to hold the test cover in position.

2. At pressure taps (A), (B), (C), (E), (F), (G), and (H), connect pressure gauges [3400 kPa (580 psi)] to the nipples.

Pressure Test Gauge Installation
(A) Pressure tap for No. 4 clutch. (B) Pressure tap for No. 2 clutch. (C) Pressure tap for No. 1 clutch. (D) Not used. (E) Pressure tap for No. 5 clutch. (F) Pressure tap for No. 6 clutch. (G) Pressure tap for No. 7 clutch. (H) Pressure tap for No. 3 clutch. (M) Pressure tap for pilot oil.

3. Start and run the engine at LOW IDLE rpm in NEUTRAL.

4. Make a record of the pressures on the gauges. Use the Maximum Clutch Pressure Measurement chart to record measurements.

5. Use the .25 (1/4) inch square drive ratchet and extension. Move transmission rotary selector spool (5) to REVERSE position.

6. Make a record of the pressures on the gauges. Use the Maximum Clutch Pressure Measurement chart to record measurements.

7. Manually shift the transmission into all forward speeds and make a record of the pressures on the gauges for each shift. Use the Maximum Clutch Pressure Measurement chart to record measurements.

8. With the transmission still in FIFTH speed, increase the engine rpm to the Maximum Governor Setting (HIGH IDLE).

9. Make a record of the pressures on the gauges. Use the Maximum Clutch Pressure Measurement chart to record measurements.

10. Decrease engine rpm to the Minimum Governor Setting (LOW IDLE) and manually shift the transmission to FOURTH speed. Increase engine rpm again to the Maximum Governor Setting. Make a record of the pressures on the gauges. Use the Maximum Clutch Pressure Measurement chart to record measurements.

11. Do Step 10 again in all speeds including REVERSE and NEUTRAL. Make sure to decrease engine rpm before each downshift is made.

12. Stop the engine with the transmission rotary selector spool in NEUTRAL.

13. Make a comparison of the actual clutch pressures recorded on the Maximum Clutch Pressure Measurement chart, with the specifications given in the Maximum Clutch Pressure Specifications chart.

14. After the problem is corrected, remove the test equipment.

Pressure Control Group
(9), (10), (11), (12), (13), (14) and (15) Modulation reduction valves. (16) Selector piston plugs (seven). (17) Load piston orifice (seven). (18) Decay orifice plug (six). (19) Load piston plug (seven). (20) Spring [inner (seven)]. (21) Spring [outer (seven)]. (22) Shims (seven places). (A), (B), (C), (D), (E), (F), (G) and (H) Pressure taps (also load piston body identification).

Problem 1:

Pressures at ALL clutches are 0 kPa (0 psi).

Probable Cause:

Pilot pressure. Do Test 3.

Problem 2:

Pressures at ALL clutches are too low.

Probable Cause:

Pilot pressure. Do Test 3.

Problem 3:

Pressure at ONE clutch is 0 kPa (0 psi).

Probable Cause:

Selector piston plug (16) is not installed.

Problem 4:

Pressure in a clutch does not increase above primary pressure.

Probable Cause:

a. Load piston plug (19) not installed.

b. Load piston orifice (17) is plugged.

c. Broken spring(s) (20, 21) in the modulation reduction valve.

Problem 5:

An additional clutch gets pressure oil in some speeds (too many clutches are engaged).

Probable Cause:

Do Test 5.

Problem 6:

Pressure in one clutch at HIGH IDLE rpm is not correct, but primary pressure in the same clutch is correct.

Probable Cause:

Do Test 5.

Problem 7:

Primary pressure in one clutch is not correct, but pressure in the same clutch at HIGH IDLE rpm is correct.

Probable Cause:

Do Test 5.

Problem 8:

Pressure in one clutch at HIGH IDLE rpm is correct, but pressure in the same clutch at LOW IDLE rpm is not correct (too low).

Probable Cause:

Bad seals in a clutch of the transmission.

Problem 9:

Pressure in one clutch does not decrease rapidly or low (approximately primary) pressure remains (stays) in one clutch.

Probable Cause:

a. Decay orifice (18) is plugged.

b. Drain orifice in rotary selector spool (5) is plugged.

Test 5. Primary Clutch Pressures

This test will show if:

The clutch pressures are adjusted correctly.

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Make reference to the WARNING given in Test 4.

Procedure:

NOTE: Use the Procedure To Manually Shift The Transmission With The Engine Running (Drive Axles Removed) given in Test 4.

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NOTICE

Make sure the drive axles on the machine are removed for this test or the clutches of the transmission will be damaged.

1. If 6V-6064 Transmission Test Cover is used, remove small cover from the top of the transmission case. If FT1874 Transmission Test Cover is used, remove the large cover from the transmission case.

2. Remove seven load piston plugs (19) from their bodies.

3. Put the test cover back in position and install four bolts to hold it in place.

4. At pressure taps (A), (B), (C), (E), (F), (G) and (H), connect pressure gauges [1000 kPa (145 psi)] to the nipples.

5. Start and run the engine at LOW IDLE rpm in NEUTRAL.

6. Make a record of the pressures on the gauges. Use the Primary Clutch Pressure Measurement chart to record measurements.

7. Use the .25 (1/4) inch square drive ratchet and extension. Move the transmission rotary selector spool to REVERSE position.

8. Make a record of the pressures on the gauges. Use the Primary Clutch Pressure Measurement chart to record measurements.

9. Manually shift the transmission into and all forward speeds and make a record of the pressures on the gauges for each shift.

10. Stop the engine with the transmission rotary selector spool in NEUTRAL.

11. Make a comparison of the actual primary clutch pressure, recorded on the Primary Clutch Pressure Measurement chart and the specification for each clutch given in the Primary Clutch Pressure Specifications chart.

12. After the problem is corrected, remove the pressure gauges and test cover. Install load piston plugs (19).

13. Install large cover, small cover and the solenoid guard. Connect the wiring harness to the solenoids.

Problem 1:

Pressure at one clutch is 0 kPa (0 psi).

Probable Cause:

Selector piston plug (16) is not installed.

Problem 2:

Primary pressures at all clutches are 0 kPa (0 psi).

Probable Cause:

Pilot pressure. Do Test 3.

Problem 3:

Primary pressures at all clutches are too low.

Probable Cause:

Pilot pressure. Do Test 3.

Problem 4:

Primary pressure at one clutch is too low.

Probable Cause:

Add shims (22) for the modulation reduction valve of the clutch that has low pressure. See Shim Chart for Pressure Control Group.

Problem 5:

Primary pressure at ONE clutch is too high.

Probable Cause:

Remove shims (22) for the modulation reduction valve that has high pressure. See Shim Chart For Pressure Control Group.

Problem 6:

An additional clutch gets pressure oil in some speeds (too many clutches are engaged).

Probable Cause:

a. A selector piston is stuck (will not go back to its original position).

b. Weak or broken inner spring (20) for the modulation reduction valve.

Problem 7:

Pressure in one clutch at HIGH IDLE rpm is not correct, but primary pressure in the same clutch is correct.

Probable Cause:

a. Wrong outer spring(s) (21) installed in the modulation reduction valve.

b. Weak or broken outer spring(s) (21) in the modulation reduction valve.

c. Load piston orifice (17) is plugged.

Problem 8:

Primary pressure in one clutch is not correct, but pressure in the same clutch at HIGH IDLE rpm is correct.

Probable Cause:

a. Wrong outer spring(s) (21) installed in the modulation relief valve.

Differential And Final Drives Troubleshooting

Visual Checks

Use these Visual Checks as a guide to troubleshooting a problem. Make the checks with the engine OFF and the parking brakes ON. During these checks, use a magnet to separate ferrous particles from non-ferrous particles (O-ring seals, bronze, etc.).

Check 1:

Remove the fill plug and check the oil level in each final drive. Make sure that the drain plug is down (in its lowest position) as shown, when the oil level is checked. Check for oil leakage on the rear tires and wheels.

Drain Plug And Fill Plug For A Final Drive (Typical Example)

Problem 1:

The oil level in a final drive is too high. The oil level in the hydraulic oil tank is too low.

Probable Cause:

Brake cooling oil leaks into final drive. Failure of small Duo-Cone seal at the rear wheel brake. Drain final drive and add new oil after a new seal is installed.

Problem 2:

The oil level in a final drive is too low.

Probable Cause:

Failure of O-ring seal on final drive housing.

Check 2:

Remove the fill plug and check the oil level in the rear axle housing. Check for leakage under the housing.

Drain Plug And Fill Plug For Rear Axle Housing

Problem 1:

The oil level in the rear axle housing is too high. The oil level in a final drive was too high also (Check 1).

Probable Cause:

Failure of small Duo-Cone seal at the rear wheel brake. Drain rear axle housing and add new oil after a new seal is installed.

Check 3:

Drain both final drives. Remove the covers to inspect for damaged gears, bearings, etc.

Check 4:

Drain the rear axle housing of differential and bevel gear oil. Remove the fill plug and check the bevel gear and pinion for damage. Look in the bottom of the rear axle housing for metal chips. Lift one rear wheel of the machine off the ground. Turn the wheel forward and backward to check the backlash (free movement) in the differential. See the Specifications for the correct amount of backlash.