515 Wheel Skidder and 525 Wheel Skidder Power Train Caterpillar

Illustration 1	g00507163
Schematic for the Transmission Hydraulic System (1) Flow control valve (2) Transmission hydraulic control valve (3) Selector spool and slug (Forward High) (4) No. 1 solenoid (Forward High) (5) Selector spool and slug (Forward Low) (6) No. 2 solenoid (Reverse) (7) Selector spool and slug (Reverse) (8) No. 3 solenoid (Forward Low) (9) Check valve (10) Screen orifice (11) Modulating relief valve (12) Slug (13) Differential relief valve (14) Spring (15) Poppet (16) Load piston springs (17) Load piston (18) Converter backflow check valve (19) Selector spool and slug (First Speed) (20) Transmission oil filter (21) Transmission dump valve (22) Transmission oil pump (23) No. 4 solenoid (First Speed) (24) Selector spool and slug (Second Speed) (25) Selector spool and slug (High Speed) (26) No. 5 solenoid (Second Speed) (27) No. 6 solenoid (Third Speed) (28) Torque converter inlet relief valve (29) Suction screen and magnet (30) Torque converter (31) Transmission lubrication (32) Oil cooler

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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.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause 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.

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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, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates.

Operational Checks

Operate the machine in each direction and in all speeds. Note the noises that are not normal and find the sources of the noises. If the machine is not operating correctly, refer to the "Troubleshooting Problem List" below.

Troubleshooting Problem List

• The transmission does not operate in any speed or the transmission slips in all speeds.

• The transmission overheats.

• Pump noise is not normal.

• Noise in the transmission is not normal.

• The transmission operates in FORWARD only.

• The four-speed transmission operates in REVERSE and in THIRD SPEED FORWARD and FOURTH SPEED FORWARD only.

• The four-speed transmission operates in REVERSE and in FIRST SPEED FORWARD and SECOND SPEED FORWARD only.

• The four-speed transmission does not operate in FIRST SPEED REVERSE, or in FIRST SPEED FORWARD.

• The four-speed transmission does not operate in THIRD SPEED REVERSE and FOURTH SPEED FORWARD.

• The four-speed transmission does not operate in SECOND SPEED FORWARD and THIRD SPEED FORWARD, or in SECOND SPEED REVERSE.

• The five speed transmission operates in REVERSE and in SECOND SPEED FORWARD, FOURTH SPEED FORWARD, and FIFTH SPEED FORWARD only.

• The five speed transmission operates in REVERSE and in FIRST SPEED FORWARD and THIRD SPEED FORWARD only.

• The five speed transmission does not operate in FIRST SPEED FORWARD and SECOND SPEED FORWARD, or in FIRST SPEED REVERSE.

• The five speed transmission does not operate in THIRD SPEED FORWARD and FOURTH SPEED FORWARD, or in SECOND SPEED REVERSE.

• The five speed transmission does not operate in FIFTH SPEED FORWARD, or in THIRD SPEED REVERSE.

• Pressure is low at speed clutch pressure tap P1 and at direction clutch pressure tap P2 when the machine is operated in all directions and in all speeds.

• Pressure is low at direction clutch pressure tap P2 when the machine is operated in REVERSE speeds.

• Pressure is low at direction clutch pressure tap P2 when the machine is operated in FORWARD speeds.

• Pressure is high at speed clutch pressure tap P1 and at direction clutch pressure tap P2 when the machine is operated in all directions and in all speeds.

• The pressure differential between P1 and P2 is not correct.

• Clutch engagement is sudden. (This causes jerky shifting.)

• Clutch engagement is slow. (This causes slow shifting in all gears.)

• Clutch engagement is slow in all FORWARD gears, in all REVERSE gears, or in any one gear speed (FORWARD and REVERSE).

• There is a loss of power when the transmission is shifted from FIFTH SPEED to FIRST SPEED.

• The transmission neutralizer is actuated and the transmission remains engaged.

• Even though the transmission engages, the machine does not move and the engine lugs.

• The engine is running and the parking brake is engaged. However, the action alarm does not sound when the transmission is put into the FORWARD direction or into the REVERSE direction.

• The backup alarm does not sound when the transmission is put in REVERSE.

• Stall speed is low.

• Stall speed is high when the machine is operated in both directions.

• Stall speed is high when the machine is operated in one direction or in one speed.

• The lubrication pressure is low.

• The lubrication pressure is high.

• Torque converter pressure is high.

• Torque converter pressure is low.

• The torque converter overheats.

• There is constant noise in the differential.

• Noise occurs in the differential at different intervals.

• Noise only occurs during turns.

• Lubricant is leaking.

• The drive wheels do not turn, but the universal joint turns.

• The front differential lock and the rear differential lock do not operate.

• The front differential lock does not operate.

• The rear differential lock does not operate.

• Low oil pressure to the winch.

Troubleshooting

Note: When components are called out in the following section, refer to Illustration 1.

Reference: This machine has a transmission electronic control. Refer to the Service Manual module Systems Operation/Testing and Adjusting, SENR6686, "515 and 525 Wheel Skidders Transmission and Grapple Electronic Control System" for information about troubleshooting the transmission electronic control.

Probable Causes of Power Train Problems

Problem

The transmission does not operate in any speed or the transmission slips in all speeds.

Probable causes

1. The transmission fuse is missing or broken.

2. There is a problem in the electrical circuit for the transmission.

3. The system voltage is low.

4. The transmission direction and speed control is faulty.

5. Oil pressure is low. This may be caused by any of the following conditions:

   1. Oil level is low.

   2. An oil strainer is dirty or there is a restriction in the oil flow circuit.

   3. An oil pump failed.

   4. Air is leaking on the inlet side of the pump.

   5. There is leakage inside the transmission (worn seals around the clutch shaft or around the clutch piston).

   6. Modulating relief valve (11) is stuck open.

6. There is a torque converter failure.

7. There is a mechanical failure in the transmission.

8. Clutch discs and clutch plates are excessively worn.

9. The transmission neutralizer switch is not operating.

10. Check valve (9) is stuck open.

Problem

The transmission overheats.

Probable causes

1. Coolant level in the radiator is low.

2. The machine is being used for the wrong application. There is too much torque converter slip, which is caused by too much load.

3. Incorrect transmission gear is being used for the load that is on the machine. Shift to a lower gear.

4. The temperature gauge is faulty.

5. The oil level is incorrectly high or low.

6. The oil cooler or oil lines are restricted.

7. The clutch slips too much. This may be caused by any of the following conditions:

   1. Oil pressure is low.

      Note: For the probable causes of low oil pressure, refer to Cause 5 in the problem "The transmission does not operate in any speed or the transmission slips in all speeds".

   2. A clutch is damaged.

8. Oil flow is low. This may be caused by pump wear or by leakage in the hydraulic system.

9. There is air in the oil. This may be caused by air leaks on the intake side of the pump.

10. Torque converter inlet relief valve (28) is stuck open. This causes low oil flow through the torque converter.

11. The clutch or clutches are not fully released. (This is called clutch drag.) This may be caused by any of the following conditions:

    1. Plates and/or discs are warped.

    2. A return spring is broken or weak.

Problem

Pump noise is not normal.

Probable causes

1. A loud noise at short intervals indicates that foreign material is in the transmission hydraulic system.

2. A constant loud noise indicates pump failure.

3. There is air at the inlet side of the pump.

Problem

Noise in the transmission is not normal.

Probable causes

1. Transmission components are worn or damaged.

   1. Gears are damaged.

   2. Teeth on the clutch plates and/or on the clutch discs are worn.

   3. Clutch plates are slipping and the clutch discs are making noise.

   4. Other transmission components are worn or damaged.

Problem

The transmission operates in FORWARD only.

Probable causes

1. Number 2 REVERSE clutch solenoid (6) is inoperative.

2. There is a problem in the electrical circuit.

3. The REVERSE clutch is not engaged or the REVERSE clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates have too much wear.

   3. Clutch components are broken.

4. Selector spool (7) is stuck.

Problem

The four-speed transmission operates in REVERSE and in THIRD SPEED FORWARD and FOURTH SPEED FORWARD only.

Probable causes

1. Number 3 FORWARD LOW clutch solenoid (8) is inoperative.

2. There is a problem in the electrical circuit.

3. The FORWARD LOW clutch is not engaged or the FORWARD LOW clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (5) is stuck.

Problem

The four-speed transmission operates in REVERSE and in FIRST SPEED FORWARD and SECOND SPEED FORWARD only.

Probable causes

1. Number 1 FORWARD HIGH clutch solenoid (4) is inoperative.

2. There is a problem in the electrical circuit.

3. The FORWARD HIGH clutch is not engaged or the FORWARD HIGH clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (3) is stuck.

Problem

The four-speed transmission does not operate in FIRST SPEED REVERSE and FIRST SPEED FORWARD.

Probable causes

1. Number 4 FIRST SPEED clutch solenoid (23) is inoperative.

2. There is a problem in the electrical circuit.

3. The FIRST SPEED clutch is not engaged or the FIRST SPEED clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (19) is stuck.

Problem

The four-speed transmission does not operate in THIRD SPEED REVERSE, or in FOURTH SPEED FORWARD.

Probable causes

1. Number 6 THIRD SPEED clutch solenoid (27) is inoperative.

2. There is a problem in the electrical circuit.

3. The THIRD SPEED clutch is not engaged or the THIRD SPEED clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (25) is stuck.

Problem

The four-speed transmission does not operate in SECOND SPEED FORWARD, and THIRD SPEED FORWARD, or in SECOND SPEED REVERSE.

Probable causes

1. Number 5 SECOND SPEED clutch solenoid (26) is inoperative.

2. There is a problem in the electrical circuit.

3. The SECOND SPEED clutch is not engaged or the SECOND SPEED clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (24) is stuck.

The five speed transmission operates in REVERSE and in SECOND SPEED FORWARD, FOURTH SPEED FORWARD, and FIFTH SPEED FORWARD only.

Probable causes

1. Number 3 FORWARD LOW clutch solenoid (8) is inoperative.

2. There is a problem in the electrical circuit.

3. The FORWARD LOW clutch is not engaged or the FORWARD LOW clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (5) is stuck.

Problem

The five speed transmission operates in REVERSE and in FIRST SPEED FORWARD and THIRD SPEED FORWARD only.

Probable causes

1. Number 1 FORWARD HIGH clutch solenoid (4) is inoperative.

2. There is a problem in the electrical circuit.

3. The FORWARD HIGH clutch is not engaged or the FORWARD HIGH clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (3) is stuck.

Problem

The five speed transmission does not operate in FIRST SPEED FORWARD and SECOND SPEED FORWARD, or in FIRST SPEED REVERSE.

Probable causes

1. Number 4 FIRST SPEED clutch solenoid (23) is inoperative.

2. There is a problem in the electrical circuit.

3. The FIRST SPEED clutch is not engaged or the FIRST SPEED clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (19) is stuck.

Problem

The five speed transmission does not operate in THIRD SPEED FORWARD and FOURTH SPEED FORWARD, or in SECOND SPEED REVERSE.

1. Number 5 SECOND SPEED clutch solenoid (26) is inoperative.

2. There is a problem in the electrical circuit.

3. The SECOND SPEED clutch is not engaged or the SECOND SPEED clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (24) is stuck.

Problem

The five speed transmission does not operate in FIFTH SPEED FORWARD, or in THIRD SPEED REVERSE.

Probable causes

1. Number 6 THIRD SPEED clutch solenoid (27) is inoperative.

2. There is a problem in the electrical circuit.

3. The THIRD SPEED clutch is not engaged or the THIRD SPEED clutch slips. This may be caused by any of the following conditions:

   1. Oil pressure is low due to leaking piston seals or due to leaking shaft seals.

   2. The clutch discs and clutch plates are worn.

   3. Clutch components are broken.

4. Selector spool (25) is stuck.

Problem

Pressure is low at speed clutch pressure tap P1 and at direction clutch pressure tap P2 when the machine is operated in all directions and in all speeds.

Probable causes

1. Modulating relief valve (11) is stuck.

2. Oil pressure is low.

   Note: For the probable causes of low oil pressure, refer to Cause 5 in the problem "The transmission does not operate in any speed or the transmission slips in all speeds".

3. Springs of load piston (16) are weak or damaged. Springs or spacers are missing.

4. Transmission dump valve (21) is stuck open.

5. Flow control valve (1) is stuck open.

6. Check valve (9) is stuck open.

Problem

Pressure is low at direction clutch pressure tap P2 when the machine is operated in REVERSE speeds.

Probable causes

There is excessive leakage in the piston seals or in the shaft seals of the REVERSE clutch.

Problem

Pressure is low at direction clutch pressure tap P2 when the machine is operated in FORWARD speeds.

Probable causes

There is excessive leakage in the piston seals or in the shaft seals of the FORWARD clutch.

Problem

Pressure is high at speed clutch pressure tap P1 and at direction clutch pressure tap P2 when the machine is operated in all directions and in all speeds.

Probable causes

1. Modulating relief valve (11) is sticking.

2. Load piston (17) is stuck.

3. The wrong load piston springs (16) are being used.

4. Slug (12) is worn. The bore for the modulating relief valve (11) is worn.

Problem

The pressure differential between P1 and P2 is not correct.

Probable causes

1. Differential relief valve (13) is not operating correctly. This may be caused by any of the following conditions:

   1. Spring (14) is weak or damaged.

   2. The wrong spring (14) was installed.

   3. Poppet (15) is faulty.

   4. Flow control valve (1) is stuck in the close position.

Problem

Clutch engagement is sudden. (This causes jerky shifting.)

Probable causes

1. Differential relief valve (13) is not operating correctly. This may be caused by any of the following conditions:

   1. Spring (14) is weak or damaged.

   2. The wrong spring (14) was installed.

   3. Poppet (15) is faulty.

2. Load piston (17) is stuck.

3. The wrong load piston springs (16) are being used or the load piston springs are damaged.

4. Transmission dump valve (21) is stuck in the closed position.

5. Converter backflow check valve (18) is not seating or the converter backflow check valve is missing.

Problem

Clutch engagement is slow. (This causes slow shifting in all gears.)

Probable causes

1. Check valve (9) is not closing or check valve (9) is open to the drain. Screen orifice (10) for the load piston is dirty or plugged.

2. Oil pressure is low.

   Note: For the probable causes of low oil pressure, refer to Cause 5 in the problem "The transmission does not operate in any speed or the transmission slips in all speeds".

3. Load piston springs (16) are weak or damaged.

4. Modulating relief valve (11) is stuck.

Problem

Clutch engagement is slow in all FORWARD gears, in all REVERSE gears, or in any one gear speed (FORWARD and REVERSE).

Probable causes

Clutch pressure is low because of leaking seals on the piston or on the shaft for the affected gear.

Problem

There is a loss of power when the transmission is shifted from FIFTH SPEED to FIRST SPEED.

Probable causes

The return spring for selector spool (25) is broken or missing. The two clutches are engaged incorrectly.

Problem

The transmission neutralizer is actuated and the transmission remains engaged.

Probable causes

1. The transmission neutralizer switch has failed.

2. The transmission direction and speed control is faulty.

Problem

Even though the transmission engages, the machine does not move and the engine lugs.

Probable causes

1. The service brakes are locked up.

2. The parking brake is not released. Also, the parking brake may be locked up.

3. There is a mechanical failure in a differential (front differential or rear differential).

4. There is a mechanical failure in a final drive.

5. Gears in the transmission do not turn because there is a mechanical failure in the transmission.

Problem

The engine is running and the parking brake is engaged. However, the action alarm does not sound when the transmission is put into the FORWARD direction or into the REVERSE direction.

Probable causes

1. The action alarm has failed.

2. There is a problem in the electrical circuit.

Problem

The backup alarm does not sound when the transmission is put in REVERSE.

Probable causes

1. The backup alarm has failed.

2. There is a problem in the electrical wiring.

3. The transmission direction control switch is faulty.

4. The transmission electronic control module is faulty.

Problem

Stall speed is low.

Probable causes

1. Engine performance is not correct.

2. The oil is cold.

Problem

Stall speed is high when the machine is operated in both directions.

Probable causes

1. Oil level is low.

2. There is air in the oil.

3. Direction clutches are slipping.

4. There is a failure in the torque converter.

Problem

Stall speed is high when the machine is operated in one direction or in one speed.

Probable causes

1. There is a leak in the clutch circuit.

2. There is a failure in the direction clutch or in the speed clutch that has high stall speed.

Problem

The lubrication pressure is low.

Probable causes

1. The torque converter inlet relief valve (28) is bypassing excessive oil flow.

2. Oil pressure is low.

   Note: For the probable causes of low oil pressure, refer to Cause 5 in the problem "The transmission does not operate in any speed or the transmission slips in all speeds".

Problem

The lubrication pressure is high.

Probable causes

The lubrication holes in the clutch shafts are blocked.

Problem

Torque converter pressure is high.

Probable causes

1. There is a restriction inside the torque converter.

2. There is a restriction in an oil passage or in the oil cooler.

Problem

Torque converter pressure is low.

Probable causes

1. The torque converter inlet relief valve (28) is bypassing excessive oil flow.

2. Oil pressure is low.

   Note: For the probable causes of low oil pressure, refer to Cause 5 in the problem "The transmission does not operate in any speed or the transmission slips in all speeds".

Problem

The torque converter overheats.

Probable causes

1. The machine is being used for the wrong application. Excessive load on the machine will cause a large amount of torque converter slip.

2. Incorrect transmission gear is being used for the load that is on the machine. Shift to a lower gear.

3. The oil level in the transmission is incorrectly high or low.

4. The coolant level in the engine radiator is low.

5. The oil cooler or oil lines are restricted.

6. Oil flow through the torque converter is low. This may be caused by any of the following conditions:

   1. The torque converter inlet relief valve (28) is bypassing excessive oil flow.

   2. Pump flow or oil pressure is low.

      Note: For the probable causes of torque converter that overheats, refer to Cause 5 in the problem "The transmission does not operate in any speed or the transmission slips in all speeds".

Problem

There is constant noise in the differential.

Probable causes

1. The level of lubricant is incorrectly high or low.

2. The wrong type of lubricant is being used.

3. Wheel bearings are damaged or improperly adjusted.

4. The ring gear and the pinion do not have correct tooth contact.

5. The ring gear and the pinion are damaged or worn.

6. The pinion to gear backlash is excessive or the pinion to gear backlash is insufficient.

7. Pinion bearings are loose or worn.

8. Side bearings are loose or worn.

Problem

Noise occurs in the differential at different intervals.

Probable causes

1. Ring gear does not run evenly because the bolts on the ring gear are not tight or the ring gear is warped.

2. Differential bearings are loose or broken.

Problem

Noise only occurs during turns.

Probable causes

1. Differential pinion gears are too tight on the retainer pins or on the pinion shaft.

2. Side gears are tight in the differential case.

3. Differential pinion gears or side gears are faulty.

4. Thrust washers are damaged or worn.

5. There is excessive backlash between the side gears and the pinion gears.

Problem

Lubricant is leaking.

Probable causes

1. Loss of lubricant through the axle shafts can be caused by any of the following conditions:

   1. Lubricant is above the proper level.

   2. The wrong type of lubricant is being used.

   3. There is a restriction in the axle housing breather.

   4. An oil seal on the axle shaft is worn or installed incorrectly.

2. Loss of lubricant at the pinion shaft can be caused by the following conditions:

   1. Lubricant is above the proper level.

   2. The wrong type of lubricant is being used.

   3. There is a restriction in the axle housing breather.

   4. An oil seal on the pinion shaft is worn or installed incorrectly.

   5. A universal joint flange is loose on the pinion shaft.

Problem

The drive wheels do not turn but the universal joint turns.

Probable causes

1. An axle shaft is broken.

2. Ring gear teeth are damaged.

3. The side gear or the differential pinion is broken.

4. The differential pinion shaft or the retainer pin is broken.

Problem

The front differential lock and the rear differential lock do not operate.

Possible Causes

1. The fuse for the differential lock is open.

2. The differential lock switch is faulty.

3. The differential lock solenoid valve is inoperative.

Front differential lock does not operate.

Possible Causes

1. There is a problem in the electrical circuit.

2. The front differential lock solenoid valve is inoperative.

3. The discs in the differential lock clutch are worn.

4. Low oil pressure:

   1. The differential lock oil filter is plugged.

5. The setting on the differential relief valve is low.

6. The seals in the differential lock clutch piston are worn.

7. The rotating seals in the differential lock are damaged.

8. The shaft end is worn on the differential lock pump.

Problem

Rear differential lock does not operate.

Possible Causes

1. There is a problem in the electrical circuit.

2. The rear differential lock solenoid valve is inoperative.

3. The discs in the differential lock clutch are worn.

4. Low oil pressure:

   1. The differential lock oil filter is plugged.

5. The setting on the differential relief valve is low.

6. The seals in the differential lock clutch piston are worn.

7. The rotating seals in the differential lock are damaged.

8. The cover end is worn on the differential lock pump.

Problem

Low oil pressure to the winch.

400 Series Winch

Possible Causes

1. The rear differential lock oil filter plugged.

2. The setting on the differential relief valve is low.

3. The setting on the winch pressure reducing valve is low.

4. The cover end is worn on the differential lock/winch pump.

C-500 Series Winch

Possible Causes

1. The control cable needs adjusting.

2. The oil filter for the winch is plugged.

3. The setting on the winch relief valve is low.

4. The cover end is worn on the differential lock/winch pump.