Procedure to Improve the Downshift on Series H Compact Wheel Loaders{3159, 4350, 4355, 7610, 7620} Caterpillar

Compact Wheel Loader:

906H (S/N: TPE1-UP)

907H (S/N: MJF1-UP)

908H (S/N: MXF1-UP)

Introduction

This Special Instruction details the procedure in order to troubleshoot the 35 km/h (22 mph) machine. Use the following procedure in order to troubleshoot the downshift from the high range to the low range.

Safety Section

Show/hide table

Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

Show/hide table

Escaping fluid under pressure, even a pinhole 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. Always use a board or cardboard when checking for a leak.

Procedure to Troubleshoot the 35 km/h (22 mph) Machine (Speeder Assembly)

Following is a list of possible causes for a failed shift. The possible causes should be reviewed in the order that is given. See ""Detailed Solutions for the Failure of Low Gear Shift " " for a detailed explanation of the causes that are listed below.

1. Improper shifting (operator error)

2. Need to update the machine software with the improvements of two speed shift.

3. Active diagnostics are present.

4. The brake pedal is unable to achieve 50 percent of position.

5. The speed control switch (cab) has failed or the wiring harness is faulty.

6. The position switch for the transmission has failed or the wiring harness is faulty.

7. The position switch for the transmission is incorrectly adjusted.

8. Hydraulic control valve for the gearshift

9. The stops for the shift rail need adjustment.

10. The piston seal is leaking in the shift cylinder or the breather for the cylinder is blocked.

11. A failure in the transmission (internal problem)

12. The Electronic Control Module (ECM) has failed.

Detailed Solutions For the Failure of Low Gear Shift

Improper Shifting (Operator Error)

If the machine functions properly, the conditions that are mentioned below must be met in order to shift the transmission properly:

• DECEL pedal must be fully depressed.

• Transmission input speed is 0 rpm.

• The gear change requested using the gear switch in the cab.

Need to Update the Machine Software with the Improvement of Two Speed Shift

If the machine is installed with one of the part numbers that are listed below, use a latest version of the machine software. Refer to "Service Software Files" in the Service Information System (SIS) for the latest upgrade:

• 298-6435 Machine Software Gp

• 317-1441 Machine Software Gp

• 324-5101 Machine Software Gp

Active Diagnostics Are Present

Diagnostics on the following components may create other problems during shifting the transmission. Any active diagnostics on the following components should be resolved. Refer to Troubleshooting, KENR5968, "Diagnostic Code Procedures" in order to troubleshoot the following components:

• The sensor for the brake is faulty. (CID 2305)

• Transmission gear sensor (CID 0700)

• Transmission range select switch (CID 1711)

• The forward/reverse switch of the joystick control is faulty. (CID 0623)

• The solenoid for the drive pump swashplate has failed. (CID 2714)

• Forward solenoid failure. (CID 2730)

• Reverse solenoid failure. (CID 2731)

• The motor solenoid has failed. (CID 2715)

• The drive motor speed sensor (CID 2775 or CID 2776)

The Brake Pedal Is Unable to Achieve 50 Percent of Position

Show/hide table

Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

As required, apply the brake in order to shift the gear. In Electronic Technician (ET), the brake pedal position sensor must be at least 50 per cent when the brake pedal is fully depressed. If this cannot be achieved then the following should be done:

• When you move the brake pedal, ensure that the brake pedal position changes the value in the electronic tool. If the values are not changed, ensure that the brake pedal is assembled properly.

• Check the calibration of the pedal with the ET service tool. Follow the instructions on the screen in order to perform the calibration.

The Speed Control Switch (Cab) Has Failed or the Wiring Harness Is Faulty

The switch for the gear change that is inside the cab should be checked. Refer to Illustration 1 for the schematic diagram of the system. The state of this switch can be verified in ET. Refer to Troubleshooting, KENR5968, "Diagnostic Code Procedures" for the detailed troubleshooting procedure.

Illustration 1	g01391924
Schematic for the transmission range select switch

The Position Switch for the Transmission Has Failed or the Wiring Harness Is Faulty

Use the following procedure in order to check the position of the transmission 293-2095 Switch by using an ET or a multimeter.

Illustration 2	g01713359
Speed control switch (gearbox) The transmission is in the low gear range when contact 4 and contact 1 are closed. The transmission is in the high gear range when contact 2 and contact 3 are closed. (1) Connector DT04-4P

1. Disconnect the switch from the wiring harness.

2. Check for continuity between contact 1 and contact 4 of the sensor. The transmission is in the first gear range when contact 4 and contact 1 are closed.

3. Press the switch and then release the sensor while you are checking for the continuity.

4. Check for continuity between contact 2 and contact 3 of the sensor. The transmission is in the second gear range when contact 2 and contact 3 are closed.

5. Press the switch and then release the sensor while you are checking for continuity.

6. Verify that the continuity check matches with the values that are in Table 1.

Illustration 3	g01694054
Transmission range select switch The upward arrow shows high gear range. The downward arrow shows low gear range. (2) Port for low gear (3) Position switch (4) Port for high gear (5) Lever

Use the following procedure in order to test the position switch for the transmission.

Manually shift the transmission with lever (5) on the side of the transmission in order to check that the position switch shows the correct gear. See Illustration 2 and Illustration 3. Use the above procedure and a multimeter in order to check the position of the gear range. You may also check the speed selector on the dash. The electronic technician will show the status of the high/low range of the gear during the shift on the basis of the position of the shift rail. Make sure that the switch is connected to the wiring harness. Check continuity of switch through the wiring harness. Refer to the electrical schematic in Illustration 2. When the shift lever is between the high gear and the low gear, the switch should be in neutral.

The Position Switch for the Transmission Is Incorrectly Adjusted

The pin 1 and pin 4 are in the closed position when the machine is low gear range. The pin 2 and pin 3 are in the closed position when the machine is high gear range. Refer to the electrical schematic in Illustration 4.

Illustration 4	g01693834
Speed control switch (gearbox) The transmission is in the low gear range when contact 4 and contact 1 are closed. The transmission is in the high gear range when contact 2 and contact 3 are closed. (1) Connector DT04-4P

Illustration 5	g01699355
Cross-sectional view shows the mounting of the position switch. (6) Support for the position switch (7) Nut

Perform the procedure below in order to check for proper adjustment of the transmission range select switch.

1. Manually change the transmission to high gear. Use lever (5) in order to manually change the transmission to the high range.

2. Turn support (6) for the switch until the bulb illuminates. The circuit is closed when the bulb is illuminated.

3. Turn the support for the switch clockwise to 1/2 turn.

4. Tighten nut (7) to the specified torque of 50 N·m (37 lb ft).

5. Manually change the transmission to low gear. Check that the low switch illuminates the test bulb.

Hydraulic Control Valve for the Gearshift

Show/hide table

Escaping fluid under pressure, even a pinhole 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. Always use a board or cardboard when checking for a leak.

Illustration 6	g01700953
(8) Speed selection solenoid valve (9) Pilot pressure supply (10) Pilot pressure test port (11) Device for shifting (gearbox) (12) A tee adapter with a test port will need to be installed on the shift cylinder at the port for high gear in order to check the pressure for the high range. (13) A tee adapter with a test port will need to be installed on the shift cylinder at the port for low gear in order to check the pressure for the low range.

Following is the list of hydraulic problems that relate to the hydraulic control valve of the gearshift:

1. Pilot pressure

   1. Check the pilot pressure (3000 kPa (435 psi)) at the speed selection solenoid valve. The part number of the shift control valve is 260-5411 Solenoid Valve and Mounting Gp .

2. Check the pressure at the shift cylinder for the high range and the low range. Tee adapters will be needed on the cylinder in order to check the pressure in the cylinder. Refer to the Illustration 6 and Illustration 3 for the locations of the test ports.

The Stops for the Shift Rail Need Adjustment

Illustration 7	g01760536
Section A-A shows the location of the shift rail.

Illustration 8	g01760634
Section A-A Cross-sectional view of the shift rail The right arrow shows the direction of sliding gear (18) for the high range (position 1). The left arrow shows the direction of sliding gear (18) for the low range (position 2). (14) Setscrew (stop for low shift rail) (15) Detent (16) Pin (command) (17) Nut (18) Plug (19) Sliding gear (20) Bolt (stop for high shift rail) (21) Breather vent

Remove the transmission in order to adjust the stops. Verify that the cylinder is in the correct position before performing the following procedure to adjust the pin (command).

1. Select the gear ratio by positioning sliding gear (19) at the end of the stroke. The right arrow shows the direction as position 1.

2. Remove breather vent (21) .

3. Loosen bolt (20) until the bolt touches plug (18). Then, turn the bolt for one-half turn in the counterclockwise direction.

4. Remove the plug (18). Keep bolt (20) in the locked position when you tighten nut (17) to the specified torque of 10 N·m (90 lb in).

5. Reinstall plug (18) and breather vent (21). Tighten breather vent (21) to the specified torque of 10 N·m (88 lb in).

6. Select the other gear ratio by moving pin (command) (16) until the end of the stroke is all the way toward the side of setscrew (14) (position 2).

7. Turn setscrew (14) until the setscrew touches the rod end. Then turn the setscrew for one-half turn in the clockwise direction.

8. Apply Loctite 542 at the end of the setscrew.

The Piston Seal Is Leaking in the Shift Cylinder or the Breather for the Cylinder Is Blocked

Show/hide table

Escaping fluid under pressure, even a pinhole 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. Always use a board or cardboard when checking for a leak.

Illustration 9	g01763253
Cross-sectional view of the shift rail (16) Pin (command) (21) Breather vent (22) O-ring seal (23) Piston (24) O-ring seal (piston seal) (25) O-ring seal (26) High side (27) Shift cylinder (28) Low side (29) Bushing

Pressurize one port of the cylinder and open the other port in order to check for failure of piston seal (24) in the shift cylinder.

1. If oil leaks out of either port then the piston seal may be damaged.

2. If oil leaks between the cylinder and the transmission, the transmission oil level will increase meaning that seal (22) between the shift cylinder and the transmission is damaged.

3. If oil leaks between the cylinder and the breather vent for the cylinder, then the breather will begin venting oil. The leakage shows that seal (25) between the shift cylinder and the breather vent is damaged.

4. The interface of the piston, the shift rail and the bushing is sealed with Loctite 520.

A Failure in the Transmission (Internal Problem)

Illustration 10	g01699364
Cross-sectional view of the shift rail (15) Detent

1. Manually change the shift rail to the high position and to the low position in order to confirm that the shaft gears will go together.

2. Remove the ball detent. Check visually or use a screwdriver to feel that the shift rail is moving when the manual lever is moved.

3. Make sure that the free movement of the lever (5) without obstructions and the locking bolt is correctly set on the lever.

4. The adjustment of the stop for the shift rail may be incorrectly set.

5. Check the transmission oil level.

6. The shift rail and the detent are jammed.

Show/hide table



Illustration 11	g01763254

7. Check the transmission oil for contamination.

   1. Remove filler plug (30) and drain plug (31) from the transmission.

8. Visually inspect the magnetic plugs. Any debris that is on the plug should be smooth when you rub the debris between the fingers. There should be no large particles.

9. Any signs of large particles or metallic debris could indicate damage to the gear.

10. If no contamination is found, replace the plugs and refill with oil.

The ECM Has Failed

Replace the ECM according to the procedure of ECM replacement, once you find no faults with the associated components or the harness. Refer to Testing and Adjusting, KENR5968, "Electronic Control Module (ECM)- Replace", for the replacement procedure of the ECM.