525C Wheel Skidder, 535C Wheel Skidder and 545C Wheel Skidder Machine Systems Caterpillar

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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.

The transmission solenoid valves direct pilot oil to the ends of the control spool. The control spool will shift allowing pressure oil to the corresponding clutches. The machine ECM activates the correct transmission solenoid valves. The speed and the direction switches send inputs to the machine ECM. For movement of the machine, two transmission solenoid valves need to be activated.

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 transmission operates in reverse and in second speed forward, fourth speed forward, and fifth speed forward only.

• The transmission operates in reverse and in first speed forward and third speed forward only.

• The transmission does not operate in first speed forward and second speed forward, or in first speed reverse.

• The transmission does not operate in third speed forward and fourth speed forward, or in second speed reverse.

• The 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).

• The transmission is shifted into NEUTRAL position 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 direction.

• 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.

• The torque converter lockup clutch does not engage.

• 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.

Troubleshooting

ReferenceThis machine has a machine Electronic Control Module (ECM). Refer to the Service Manual module Testing and Adjusting, "Electrical General Information" for information about the machine ECM.

Probable Causes of Transmission 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 control switch and/or speed control switches are 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. The modulating relief valve for the transmission 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. A Check valve in the transmission control 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 control system.

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

10. The torque converter inlet relief valve 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. The number 2 reverse clutch solenoid 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. The selector spool for reverse is stuck.

Problem

The transmission operates in reverse and in second speed forward, fourth speed forward, and fifth speed forward only.

Probable causes

1. The number 3 low forward clutch solenoid is inoperative.

2. There is a problem in the electrical circuit.

3. The low forward clutch is not engaged or the low forward 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. The selector spool for low forward is stuck.

Problem

The transmission operates in reverse and in first speed forward and third speed forward only.

Probable causes

1. The number 1 high forward clutch solenoid is inoperative.

2. There is a problem in the electrical circuit.

3. The high forward clutch is not engaged or the high forward 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. The selector spool for high forward is stuck.

Problem

The transmission does not operate in first speed forward and second speed forward, or in first speed reverse.

Probable causes

1. The number 4 first speed clutch solenoid 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. The selector spool for first speed is stuck.

Problem

The transmission does not operate in third speed forward and fourth speed forward, or in second speed reverse.

1. The number 5 second speed clutch solenoid 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. The selector spool for second speed is stuck.

Problem

The transmission does not operate in fifth speed forward or in third speed reverse.

Probable causes

1. The number 6 third speed clutch solenoid 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. The selector spool for third speed 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. The modulating relief valve 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. The springs of the load piston are weak or damaged. Springs or spacers are missing.

4. The dump valve is stuck open.

5. The flow control valve is stuck open.

6. A check valve 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. The modulating relief valve is sticking.

2. The load piston is stuck.

3. The wrong load piston springs are being used.

4. The slug inside the modulating relief valve is worn. The bore for the modulating relief valve is worn.

Problem

The pressure differential between P1 and P2 is not correct.

Probable causes

1. The differential relief valve is not operating correctly. This may be caused by any of the following conditions:

   1. The spring inside the differential relief valve is weak or damaged.

   2. The wrong spring was installed inside the differential relief valve.

   3. The poppet inside the differential relief valve is faulty.

   4. The flow control valve is stuck in the closed position.

Problem

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

Probable causes

1. The differential relief valve is not operating correctly. This may be caused by any of the following conditions:

   1. The spring inside the differential relief valve is weak or damaged.

   2. The wrong spring was installed inside the differential relief valve.

   3. The poppet inside the differential relief valve is faulty.

2. The load piston is stuck.

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

4. The dump valve is stuck in the closed position.

5. The backflow check valve for the torque converter is not seating or the backflow check valve is missing.

Problem

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

Probable causes

1. The check valve is not closing or the check valve is open to the drain. The screen orifice 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. The load piston springs are weak or damaged.

4. The modulating relief valve 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

The transmission direction control switch is shifted to the NEUTRAL position and the transmission remains engaged.

Probable causes

1. The transmission direction control switch is faulty.

2. There is a problem in the electrical circuit.

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.

3. There is a problem with the parking brake pressure switch.

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. There is a problem in the power train electronic control module (ECM).

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 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 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 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

The torque converter lockup clutch does not engage.

Probable causes

1. The switch for the lockup clutch is not in the ON position.

2. The switch for the lockup clutch is faulty.

3. The transmission output speed sensor is faulty.

4. The modulating valve or the torque converter lockup is faulty.

5. There is a problem in the electrical circuit.

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 transmission output speed sensor is faulty.

4. The differential lock solenoid is faulty.

5. The pressure reducing valve is faulty.

6. The differential lock solenoid valve is inoperative.

7. Low oil pressure.

Problem

Front differential lock does not operate.

Possible Causes

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

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

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

Problem

Rear differential lock does not operate.

Possible Causes

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

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

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