902 and 906 Compact Wheel Loaders Power Train System Caterpillar

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Personal injury or death can result from improperly checking for a leak. Always use a board or cardboard when checking for a leak. Escaping air or fluid under pressure, even a pin-hole size leak, can penetrate body tissue causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury.

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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, perform the procedure that follows before testing and adjusting the power train.

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NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates.

Note: All of the tests are run with 10W hydraulic oil at a temperature range of 38 to 65°C (100 to 150°F).

The tests for the hydraulic system should be done in the following order. In order for the hydrostatic system to function properly, each component in the system must be set to the correct specifications. Some components must be set prior to the testing of other components. A component that is not set properly will have an impact on other components in the system.

You should not bypass preceding tests. The following chart lists the equipment that is needed to perform testing on the hydrostatic system. Equivalent tooling may be substituted. You will need additional wrenches, shop equipment and tools. You may need additional fittings.

Clearly mark all of the hoses and the corresponding pressure gauges, when the hoses are installed. The hoses and the pressure gauges will be used multiple times in the testing and adjusting procedures.

Test A

Baseline for the Hydrostatic System

Test A must be performed in order to establish a starting point for the hydrostatic system. After this test has been completed, two objectives will be established. The machine will be able to be tested. A baseline for the remaining tests will have been established.

Table 1

Required Tools
Part number	Description	Quantity
8T-0861	Gauge 0 to 60000 kPa	1
8T-0860	Gauge 0 to 40000 kPa	1
8T-0855	Gauge 0 to 4000 kPa	4
8T-0853	Gauge 0 to 400 kPa	1
1U-5755	Hose	7
9U-7400 6V-3121	Multitach	2
6V-9509	Plug	2
3J-1907	O-ring	1
3J-7354	O-ring	2
6V-8398	O-ring	2
6V-9830	Cap	1
6V-4143	Coupler Assembly	14
6V-3989	Unvalved Nipple	5
6V-3966	Valved Nipple Assembly	4
6V-3965	Valved Nipple Assembly	1
1S-8937	Needle Valve	1
2D-7325	Pipe Tee	1
110-6349	Valved Nipple Assembly	2
1U-9760	Stand	4

1. Raise the engine access panel.

2. Secure all of the hydraulic lines so that the pressure gauges can be viewed by the operator during the test. Do NOT hold the pressure gauge or the hydraulic line.
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   Illustration 1	g00470422
   This is the location of the charge pressure tap.

3. Install one 8T-0855 Pressure Gauge to the charge pressure tap with a 1U-5755 Hose.
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   Illustration 2	g00470438
   This is the location of the signal pressure tap on the 902 . The pressure tap is located on the bottom of the piston pump toward the firewall.

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   Illustration 3	g00470519
   This is the location of the signal pressure tap on the 906. The pressure tap is located on the top of the piston pump toward the firewall.

4. Install one 8T-0855 Pressure Gauge to the signal pressure tap with a 1U-5755 Hose.
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   Illustration 4	g00470433
   This is the location of the pressure tap for the pump case.

5. Install one 8T-0853 Pressure Gauge to the pressure tap for the pump case with a 1U-5755 Hose.
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   Illustration 5	g00471486
   This is the location for the MH pressure tap for the drive loop.

6. Install one 8T-0861 Pressure Gauge to the MH pressure tap with a 1U-5755 Hose.
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   Illustration 6	g00472664
   This is the location for the IP pressure tap for the work tool.

7. Install one 8T-0860 Pressure Gauge to the IP pressure tap for the work tool with a 1U-5755 Hose.
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   Illustration 7	g00471167

8. Install a 6V-3121 multitach group, or install a 9U-7400 multitach group in order to measure engine rpm. Install a piece of reflective tape on the pulley for the engine crankcase. The multitach will read the engine rpm from this tape.
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   Illustration 8	g00928835

9. Install a 6V-3121 Multitach group, or install a 9U-7400 Multitach group in order to measure the fan speed. Install a piece of reflective tape on a fan blade. Use the reflective tape on the fan blade to measure the fan speed with the multitach.

10. Engage the parking brake.

11. Place the direction control switch into the NEUTRAL position.

12. Place the speed control into the SLOW position.

13. Start the engine and run the engine at low idle.

14. Record the charge pressure, the pump signal pressure, the pressure for the pump case, the fan speed and the engine rpm.

    If the engine speed for low idle is incorrect, perform the following adjustments.

    • Adjust the low idle to the correct speed.

15. Increase the engine speed to high idle.

16. Record the charge pressure, the pump signal pressure, the pressure for the pump case, and the engine rpm.

    If the engine speed for high idle is incorrect, perform the following checks.

    • If the engine speed is low, check for a parasitic load.

    • If the engine speed is high, refer to qualified personnel for adjusting the high idle.

Table 2

Test A for the 902 Test for the Baseline
Test	Low Idle		High Idle
	Spec	Actual	Spec	Actual
Engine Speed	1000 ± 25 rpm		2800 ± 50 rpm
Charge Pressure	3150 ± 350 kPa (460 ± 50 psi)		3300 ± 200 kPa (480 ± 30 psi)
Pump Signal Pressure	450 ± 200 kPa (65 ± 30 psi)		3100 ± 300 kPa (450 ± 45 psi)
Pressure for the Pump Case	30 ± 30 kPa (4 ± 4 psi)		50 ± 50 kPa (7 ± 7 psi)
Fan Speed			2150 ± 50 rpm

Table 3

Test A for the 906 Test for the Baseline
Test	Low Idle		High Idle
	Spec	Actual	Spec	Actual
Engine Speed	980 ± 25 rpm		2800 ± 50 rpm
Charge Pressure	3150 ± 350 kPa (460 ± 50 psi)		3300 ± 200 kPa (480 ± 30 psi)
Pump Signal Pressure	450 ± 200 kPa (65 ± 30 psi)		2700 ± 300 kPa (390 ± 45 psi)
Pressure for the Pump Case	30 ± 30 kPa (4 ± 4 psi)		50 ± 50 kPa (7 ± 7 psi)
Fan Speed			2150 ± 50 rpm

If the charge pressure is too low or too high at high idle, perform the following adjustments.

• Replace the charge relief valve and recheck the pressure. Make sure that the charge pressure is correct before proceeding.

If the charge pressure is too low at low idle, perform the following checks.

• The possibility exists of a large internal leak.

If the pressure of the pump case is high perform the following checks.

• Check for a restriction of the lines.

• Check the oil temperature. Make sure that the operating temperature of the oil is correct. Check the viscosity of the oil.

If the pump signal pressure is low at low idle, perform the following adjustment.

• Turn the adjustment screw on the speed sensing valve counterclockwise.

If the pump signal pressure is high at low idle, perform the following adjustment.

• Turn the adjustment screw on the speed sensing valve clockwise.

If the pump signal pressure is low at high idle, perform the following adjustments.

• Turn the adjustment screw on the speed sensing valve counterclockwise.

Note: Do not disconnect the lines or the gauges. The gauges will be used in order to check the pressures in the tests that follow. Leave the 6V-3121 Multitach connected in order to measure the engine rpm for the tests that follow.

Test B

Start to Move Test

The test determines correct speeds of the engine and the speed of the machine when the machine begins to move. The test determines if engine speeds and machine speeds are correct. If the results are not correct, repeat test A. The test can be done in either speed and the test should get the same results.

The specification that is critical is the comparison of the signal pressure to the MH pressure. The MH pressure will momentarily increase at approximately 5000 kPa (725 psi) with the engine speed about 1100 rpm. Signal pressure should be approximately 650 kPa (95 psi).

1. The gauges for charge pressure, MH pressure, and pump signal pressure should be installed on the machine. The multitach should still be on the machine. If the gauges or the multitach are not on the machine, reinstall the gauges and the multitach.

2. Engage the parking brake. Start the engine.

3. Place the speed control into the SLOW position.

4. Move the direction control switch to the FORWARD, the NEUTRAL, and the FORWARD position within three seconds. This allows you to drive through the parking brake.

5. Slowly Increase the engine rpm until MH pressure is 5000 ± 50 kPa (720 ± 10 psi).

6. Record the engine speed, the pump signal pressure, the charge pressure, and the MH pressure.
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   Table 4

   Test B For A Machine That Starts To Move in a FORWARD Direction
   Test	Spec	Actual
   Signal Pressure	550 ± 100 kPa (80 ± 15 psi)
   MH Pressure for the Drive Loop	5000 ± 100 kPa (725 ± 15 psi)
   Engine rpm	1125 ± 25 rpm
   Charge Pressure	2650 ± 750 kPa (385 ± 110 psi)

7. Move the direction control switch to NEUTRAL.

8. Move the direction control switch to the REVERSE, the NEUTRAL, and the REVERSE position within three seconds. This allows you to drive through the parking brake.

9. Slowly Increase the engine rpm until MH is 5000 ± 50 kPa (720 ± 10 psi).

10. Record the engine speed, the pump signal pressure, the charge pressure, and the MH pressure.
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    Table 5

    Test B For A Machine That Starts To Move in a REVERSE Direction
    Test	Spec	Actual
    Signal Pressure	550 ± 100 kPa (80 ± 15 psi)
    MH Pressure for the Drive Loop	5000 ± 300 kPa (720 ± 40 psi)
    Engine rpm	1125 ± 25 rpm
    Charge Pressure	2650 ± 750 kPa (385 ± 110 psi)

Perform the following check if the engine speed is low in both directions.

• Check the setting of the charge pressure. Adjust the speed sensing valve. Turn the adjustment screw counterclockwise.

Perform the following check if the engine speed is high in both directions.

• Check the setting of the charge pressure. Adjust the speed sensing valve. Turn the screw clockwise.

Test C

Stall Test

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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, perform the procedure that follows before testing and adjusting the power train.

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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

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NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates.

Test C is for the stall test for the hydrostatic system. The test is also for the work tool. Perform the test in order to determine the system that is causing a problem. The tests stall the hydrostatic system and the work tool system independently. The test can be used in order to identify low power problems with the engine. The test is also used to identify the POR valve and the crossover relief valves that are malfunctioning.

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NOTICE
Driving through the brake for more than 15 seconds may damage the brake.

Note: The condition of the brake pads may allow the machine to drive through the brakes. The condition of the rotor may allow the machine to drive through the brakes. Ensure that the brakes are in good condition before doing this test. Refer to the Testing and Adjusting, SENR1290, "Parking Brake - Test and Adjust".

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Illustration 9	g00471514

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Illustration 10	g00491200

Note: Make sure that all lines and all fittings are clean before disconnecting the signal line.

1. Disconnect the signal line for the brake valve at the piston motor ( hydrostatic). Install a plug in the signal line (1). Install a cap on the tee (2).

2. Block the wheels in order to stall the hydrostatic system.

3. Engage the parking brake.

4. Apply the service brake.

5. Start the engine and run the engine at low idle.

6. Place the speed control into the SLOW position.

7. Move the direction control switch to the FORWARD, the NEUTRAL, and the FORWARD position within three seconds. This allows you to drive through the parking brake.

8. Slowly increase the engine speed to high idle.

   Note: Movement of the wheel is not allowed.

9. Record the engine rpm and record the MH pressure for the drive loop.

Table 6

Test C Stall Test for the Hydrostatic System
Test	Spec	Actual
Engine Speed from Test C	70 ± 70 rpm or less than Test A
MH Pressure	45500 ± 1500 kPa (6600 ± 220 psi)

1. Shift the direction control switch into the NEUTRAL position.

2. Increase the engine speed to high idle.
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   NOTICE
   Do not stall the work tool for more than 15 seconds.

3. Move the work tool control to the RAISE position. Hold the control in this position until the lift arms stall.

4. Record the pressure for the work tool IP and record the engine rpm.

Table 7

Test C for the 902 Stall Test for the Work Tool
Test	Spec	Actual
Pressure for the Work Tool IP	23500 ± 1500 kPa (3400 ± 220 psi)
Engine rpm below the rpm of test A	85 ± 85 rpm

Table 8

Test C for the 906 Stall Test for the Work Tool
Test	Spec	Actual
Pressure for the Work Tool IP	24000 ± 1500 kPa (3480 ± 220 psi)
Engine rpm below the rpm of test A	65 ± 65 rpm

If the engine lug is high, perform the following check.

• The engine power may be low.

Perform the following check if the engine lug is okay for the stall of the hydrostatic system, but the engine rpm is below the specification for the stall of the work tool.

• The relief valve for the work tool may be set too high.

Perform the following check if the engine lug is okay for the stall of the work tool, but the engine lug is low for the stall of the hydrostatic system.

• The pump may have an internal leak, or the motor may have an internal leak.

• The brakes may be improperly adjusted. Look for slippage of the machine or creeping of the machine.

If the MH pressure is low and the engine rpm is not within the specification, perform the following checks.

• The POR valve is set too high.

If the MH pressure is low and the engine lug is high in one direction, perform the following checks.

• The crossover relief valve is incorrect. Replace the valve.

If the MH pressure is incorrect and the engine lug is okay perform the following checks.

• Reset the setting of the POR valve.

Perform the following checks, if the MH pressure is incorrect for one direction, but the gauge reading fluctuates for the MH pressure.

• The crossover relief valve reacts with the POR valve. Replace the crossover relief valve.

Test D

Double Stall Test

The test will determine if engine performance is low.

The signal line for the brake valve should still be disconnected.

1. Block the wheels.

2. Start the engine.

3. Engage the parking brake and apply the service brake.

4. Move the speed control to the SLOW position.

5. Increase the engine speed to high idle.

6. Move the direction control switch to the FORWARD, the NEUTRAL, and the FORWARD position within three seconds. This allows you to drive through the parking brake.

   Note: Do not stall the drive pressure for more than 15 seconds.

7. Move the work tool control to the RAISE position. Hold the control in this position until the lift arms stall.

8. Record the MH pressure, the pressure for the work tool IP, and the engine rpm.

Table 9

Test D for 902 Wheel Loader Stall Test for the Hydrostatic Drive and for the Work Tool
Test	Spec	Actual
MH Pressure	45000 ± 1500 kPa (6525 ± 220 psi)
Work Tool Pressure	23500 ± 1500 kPa (3400 ± 220 psi)
Engine rpm below the rpm of test A	300 ± 300 rpm

Table 10

Test D for 906 Wheel Loader Stall Test for the Hydrostatic Drive and for the Work Tool
Test	Spec	Actual
MH Pressure	45000 ± 1500 kPa (6525 ± 220 psi)
Work Tool Pressure	24000 ± 1500 kPa (3480 ± 220 psi)
Engine rpm below the rpm of test A	100 ± 100 rpm

If the engine rpm is not to the correct specification, perform the following checks.

• The engine power is low. Check the throttle, injectors, and fuel pressure.

• Check for a parasitic load.

Test E

Pump Neutral Setting

Perform the test in order to make sure that the pump fully destrokes. If the pump is not destroked the machine could move in the NEUTRAL position.

Note: If the machine does not move in the NEUTRAL position, this test is not required.

Table 11

Required Tools
Part number	Description	Quantity
8T-0855	Gauge 0 to 4000 kPa	2
1U-5482	Hose	2
110-6349	Nipple Assembly	2
3J-7354	O-Ring Seal	2

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Illustration 11	g00474731

1. Install the 3J-7354 O-Ring Seal to the 110-6349 Nipple Assembly. Install the 110-6349 Nipple Assembly into the MA plug (1) on the pump. Install the 110-6349 Nipple Assembly into the MB plug (2) on the pump.

2. Install one 8T-0855 Pressure Gauge to the MA pressure tap with a 1U-5755 Hose.

3. Install one 8T-0855 Pressure Gauge to the MB pressure tap with a 1U-5755 Hose.

4. Engage the parking brake.

5. Shift the direction control switch to the NEUTRAL position.

6. Move the speed control to the FAST position.

7. Start the engine and run the engine at high idle.

8. Record the pressures on the MA and the MB test port.

9. The difference in the gauge pressures should be 0 ± 50 kPa (0 ± 7 psi).
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   Illustration 12	g00917408

10. Adjust the null on the pump until the difference in the gauge pressures is 0 ± 50 kPa (0 ± 7 psi).

This is an alternate method of testing the neutral setting of the pump.

1. Connect the MA and MB test ports together with a test hose.

2. Run the engine in the NEUTRAL position at high idle.

3. Install one 8T-0855 Pressure Gauge to the MH pressure tap with a 1U-5755 Hose.
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   Illustration 13	g00917408

4. Adjust the null on the pump until the MH pressure is a minimum.

Test F Maximum Runout

Note: This test requires the tires to be removed and this test requires the machine to be placed on stands. Be sure to engage the steering frame lock.

Table 12

REQUIRED TOOLS
Part Number	Description	Quantity
1U-9760	Stands	4

The test is used to determine if the engine and the machine speeds are correct for the maximum travel speed in both speed ranges.

Run the machine at the maximum speed in the SLOW speed position and move the speed control to the FAST speed position. This checks whether the motor is destroked in the FAST speed position. If the machine speeds up, the motor is destroking. However, the motor may not be destroking enough to allow the machine to reach maximum speed.

1. Move the machine to an area that is level and a surface that is smooth and hard. Install the steering frame lock. Remove the tires. As each tire is removed, place a 1U-9760 Stand under the outer end of each axle.
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   Illustration 14	g00471167

2. Install a 6V-3121 Multitach, or install a 9U-7400 Multitach in order to measure engine rpm. Read the rpm from the reflective tape that is on the pulley for the engine crankcase.

3. Install a 6V-3121 Multitach, or install a 9U-7400 Multitach in order to measure drive shaft speed. Place a piece of reflective tape on the drive shaft. Read the rpm from the reflective tape that is on the drive shaft.

4. Disengage the parking brake. Release the service brake. Move the speed control to the SLOW speed position. Shift the direction control switch to the FORWARD position. Increase the engine rpm to high idle.

5. Record the MH pressure and the signal pressure.

6. Record the engine rpm.

7. Record the drive shaft speed.

8. Disengage the parking brake. Release the service brake. Move the speed control to the SLOW speed position. Shift the direction control switch to the REVERSE position. Increase the engine rpm to high idle.

9. Record the MH pressure and the signal pressure.

10. Record the engine rpm.

11. Record the drive shaft speed.

12. Run the machine in the FAST speed position and the FORWARD position for the test.
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    Table 13

    Test F For the 902 Compact Wheel Loader Maximum Speed Test for the Displacement Control for the Pump and the Motor In the FORWARD Direction
    Test	SLOW		FAST
    	Spec	Actual	Spec	Actual
    Signal Pressure	2900 ± 500 kPa (420 ± 75 psi)		2900 ± 300 kPa (420 ± 75 psi)
    MH Pressure for the Drive Loop	5500 ± 1050 kPa (800 ± 150 psi)		9000 ± 2000 kPa (1300 ± 290 psi)
    Engine rpm	2770 ± 35 rpm		2715 ± 35 rpm
    Drive Shaft rpm	725 ± 30 rpm		1945 + 135 / −20 rpm

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    Table 14

    Test F For The 906 Wheel Loader Maximum Speed Test for the Displacement Control for the Pump and the Motor In The FORWARD Direction
    Test	SLOW		FAST
    	Spec	Actual	Spec	Actual
    Signal Pressure	2500 ± 500 kPa (365 ± 75 psi)		2900 ± 300 kPa (365 ± 75 psi)
    MH Pressure for the Drive Loop	5650 ± 1150 kPa (820 ± 165 psi)		9000 ± 2000 kPa (1305 ± 290 psi)
    Engine rpm	2760 ± 35 rpm		2730 ± 35 rpm
    Drive Shaft rpm	780 ± 30 rpm		1770 + 125 / −20 rpm

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    Table 15

    Test F For the 902 Wheel Loader Maximum Speed Test for the Displacement Control for the Pump and the Motor In The REVERSE Direction
    Test	SLOW
    	Spec	Actual
    Signal Pressure	2900 ± 500 kPa (420 ± 75 psi)
    MH Pressure for the Drive Loop	5500 ± 1150 kPa (800 ± 165 psi)
    Engine rpm	2770 ± 35 rpm
    Drive Shaft rpm	725 ± 30 rpm

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    Table 16

    Test F For the 906 Wheel Loader Maximum Speed Test for the Displacement Control for the Pump and the Motor In The REVERSE Direction
    Test	SLOW
    	Spec	Actual
    Signal Pressure	2500 ± 500 kPa (365 ± 75 psi)
    MH Pressure for the Drive Loop	5650 ± 1150 kPa (820 ± 165 psi)
    Engine rpm	2760 ± 35 rpm
    Drive Shaft rpm	780 ± 30 rpm

Perform the following check if the pump signal pressure is not to the correct specification.

• The brake pedal may not be returning.

• The speed sensing valve may be misadjusted.

Perform the following check if the MH pressure is high in the SLOW speed.

• The axle may have a problem.

Perform the following check if the MH pressure is high for the FAST speed and the SLOW speed. Perform the following check if the pressure is high for the FORWARD and the REVERSE directions.

• The axle may have a problem.

• The parking brake may not be released.

• The brakes may be dragging or the brakes may be misaligned.

Perform the following check if the speed of the drive shaft is off in one direction. Perform the following check if the speed of the drive shaft is off for all speeds.

• The maximum stop of the motor may be misadjusted.

Perform the following check if the drive shaft speed is off in both directions. Perform the following check if the drive shaft speed is off for SLOW speed.

• The maximum stop of the motor may be misadjusted.

Perform the following check if the drive shaft speed is off in both directions. Perform the following check if the drive shaft speed is off for FAST speed.

• The minimum stop of the motor may be misadjusted.

Perform the following check if the motor speed is low in both directions. Perform the following check if the motor speed is off for FAST speed and SLOW speed.

• The engine may have low power. Check the rpm.

• The machine may be cold.

Test G Displacement Control Valve For The Motor

The test for the displacement control valve for the piston motor is used to determine if the motor is destroking and when the motor is destroking. Charge pressure is used to create the signal pressure instead of the speed sensing valve in order to get a more consistent pressure.

When a machine travels up a slope, a displacement control valve that is not correctly adjusted is more noticeable. When a machine travels on a surface that is flat, a valve that is incorrectly adjusted is more difficult to determine.

Disconnect the line for the signal pressure of the piston pump from the tee in the piston motor. Plug the line for the signal pressure from the pump. Cap the tee prior to performing the test.

Table 17

Required Tools
Part number	Description	Quantity
6V-9509	Plug	2
6V-8398	O-ring	2
3J-1907	O-ring	1
6V-9830	Cap	1
6V-3965	Valved Nipple Assembly	1
6V-3966	Valved Nipple Assembly	4
1S-8937	Needle Valve	1
2D-7325	Pipe Tee	1

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Illustration 15	g00502821

1. Install the 6V-3966 Valved Nipple Assembly (1) to the 1S-8937 Needle Valve (2). Install one 2D-7325 Pipe Tee (3) into the needle valve. Install the 6V-3966 Valved Nipple Assembly (4) and the 6V-3966 Valved Nipple Assembly (5) to the pipe tee (3).
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   Illustration 16	g00471514
   Signal line

2. Disconnect the signal line for the brake valve at the piston motor.
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   Illustration 17	g00834405
   (6) 6V-9509 Face Seal Plug with 6V-8398 O-Ring Seal (7) 6V-9830 Cap Assembly (8) 6V-9509 Face Seal Plug with 6V-8398 O-Ring Seal (9) 6V-3965 Valved Nipple Assembly

3. Install a plug into the signal line. Install a cap on the tee fitting. Disconnect the tee fitting from the motor and install a plug into the tee fitting. Install one test fitting into the motor.
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   Illustration 18	g00502821

4. Connect one end of a 1U-5755 Hose to the pressure port for the charge pressure of the pump. Install the other end of the hose to the test port (1) on the needle valve (2).

5. Install one 8T-0855 Pressure Gauge to the test port (5) on the needle valve with a 1U-5755 Hose.

6. Connect one end of a 1U-5755 Hose to test port (4) on the needle valve. Connect the other end of the hose to the test fitting that is installed on the motor.
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   Illustration 19	g00484064

7. Install one 8T-0861 Pressure Gauge to the M1 pressure tap with a 1U-5755 Hose.

8. Ensure that the steering frame lock is engaged. Block the wheels in order to stall the hydrostatic system.

9. Shut off the needle valve in order to block the charge oil.

10. Run the engine at low idle.

11. Engage the parking brake and apply the service brake.

12. Move the speed control to the FAST speed.

13. Shift the direction control switch to the FORWARD position, the NEUTRAL position, and theFORWARD within three seconds.
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    Illustration 20	g00503442

14. Very slowly open the needle valve until the charge pressure is approximately 2000 kPa (290 psi). Slowly increase the engine speed and watch the M1 pressure increase. Record the charge pressure and record the M1 pressure at the point just before the pressure falls. Record the pressures at approximately 2000 kPa (290 psi), 2500 kPa (360 psi), and 2800 kPa (400 psi).

15. If the needle valve is opened too quickly, the pressure may rise too fast in order to make a record. Move the direction control switch into the NEUTRAL position. Stop the engine. Open the needle valve in order to relieve the pressure. Wait until the charge pressure drops to zero on the gauge.

Illustration 21	g00845688
(A) M1 Pressure (B) Pump Charge Pressure at the motor. (C) Maximum (D) Nominal (E) Minimum

• If the points that are plotted are above the maximum, the motor will stroke too late causing the engine to lug. If the pressures are not within the limits, the actuator for the motor displacement must be adjusted.

• If the points that are plotted are below the minimum, the motor will stroke too soon causing the travel speed to be slow. If the pressures are not within the limits, the actuator for the motor displacement must be adjusted.

Illustration 22	g00917787

Note: Adjusting the actuator for the motor displacement will void the warranty on the piston motor.

If you need to adjust the actuator for the motor displacement, make adjustments in small increments. The relationship between M1 pressure and the actuator adjustment is not linear. Only a small amount of adjustment should be needed. Complete the test for the actuator for the piston motor after you make any adjustment to the actuator.

At the end of the test, relieve the pressures prior to removing lines, gauges and hoses. Reinstall the signal lines for the piston pump and the brake valve.