554 and 574 Forwarders Power Train 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 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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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.

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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.

Diagnostic Checks

The IQAN Monitoring and Control System should be used as the first step in troubleshooting a problem with the power train. The IQAN allows you to test the electrical signals that are inputs to the IQAN. The IQAN also allows you to test the electrical signals that are outputs from the IQAN.

Reference: For more information about the IQAN Monitoring and Control System, refer to System Operation, RENR6127, "IQAN Monitoring and Control System".

In order for a power train component to function correctly, the following conditions must exist:

• The IQAN must receive the correct electrical signal from the switch or the sensor.

• The solenoid must receive the correct electrical signal from the IQAN.

• Pilot pressure oil must flow to the valve spool for the power train component.

• System pressure oil must flow to the power train component.

When a power train component does not function correctly, perform the following steps in order to diagnose the problem:

1. Check the electrical signal from the switch or the sensor. If the IQAN does not receive the signal, check the wiring harness, switches, and control levers. If the IQAN receives the signal, continue to Step 2.

2. Check the outputs from the IQAN to the solenoids. With a stopped engine, use the IQAN to check the output to the solenoid. The magnitude of the current must be correct for the solenoid to activate. If the magnitude of the current is correct, perform Step 3.

3. Measure the current to the solenoid. Ensure that the output current from the IQAN flows to the solenoid. If output current does not flow to the solenoid, check the wiring harnesses between the IQAN and the solenoid. If the harness is ok, the IQAN module (XP, XS, or MG) should be replaced.

4. If the function continues to operate incorrectly, perform the following inspection:
   • Check the system pressure of the oil for the component.

   • Check for pilot pressure in the valve for the component.

   • Inspect the hydraulic oil lines for restrictions and leaks.

   • Inspect the components for wear and obstructions.

   • Inspect the valve spool for wear and abrasions.

The IQAN can also be used to check the operation of the sensors that are on the machine. The IQAN will display the state of the sensor.

Reference: For more information on using the IQAN for troubleshooting, refer to Systems Operation, RENR6127, "IQAN® Monitoring & Control System".

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. Also, note any warnings that appear on the IQAN screen.

If the machine is not operating correctly, refer to the "Troubleshooting Problem List" below.

Troubleshooting Problem List (Power Train)

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

2. The transmission overheats. ( 554 and 574 1FM1-433)

3. There is a noise in the power train pump that is not normal.

4. There is noise in the transmission that is not normal.

5. The transmission operates in FORWARD only.

6. The transmission operates in REVERSE only.

7. The transmission does not operate in FIRST SPEED FORWARD or in FIRST SPEED REVERSE.

8. The transmission does not operate in SECOND SPEED FORWARD or in SECOND SPEED REVERSE.

9. The transmission does not operate in THIRD SPEED FORWARD or in THIRD SPEED REVERSE.

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

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

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

13. The machine does not move and the engine lugs when the transmission is engaged.

14. There is constant noise in the differential.

15. Noise occurs in the differential at different intervals.

16. Noise only occurs during turns.

17. Lubricant is leaking.

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

19. The low oil pressure warning for the charge pressure will not turn off.

Probable Causes of Power Train Problems

Problem 1: The transmission does not operate in any speed or the transmission slips in all speeds.

Probable causes:

1. The parking brake is engaged.

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

3. The system voltage is low.

4. The speed selector switch is faulty.

5. The direction selector switch is faulty.

6. No current to the gear shift solenoids. The gearbox is mechanically disengaged. ( 554 Forwarder)

7. The oil pressure is low. This may be caused by any of the following conditions:

   1. The oil level is low.

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

   3. The oil pump has failed. ( 554 and 574 1FM1-433)

   4. Air leaks on the inlet side of the pump.

   5. There is oil leakage inside the transmission (worn seals around the clutch piston and the shift piston).

8. There is a mechanical failure in the transmission.

9. Clutch discs and clutch plates are excessively worn. ( 554 and 574, 1FM1-433)

10. The power train pump has failed.

11. The power train motor has failed.

Problem 2: The transmission overheats.

Probable causes:

1. The oil level is too high or too low.

2. The machine is being used for the wrong application. There is too much of a load.

3. An incorrect transmission speed is being used for the load that is on the machine. Shift to a lower speed.

4. The temperature sensor is faulty. ( 554 and 574, 1FM1-433)

5. The clutch slips too much. ( 554 and 574, 1FM1-433) This may be caused by any of the following conditions:

   1. Low oil pressure. Refer to "Problem: The transmission does not operate in any speed or the transmission slips in all speeds."

   2. A clutch is damaged.

6. Oil flow is low. This may be caused by pump wear or by oil leakage.

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

8. The gearshift solenoid is faulty. ( 574, 1FM434-UP)

9. No oil pressure to the gearshift cylinder. ( 574, 1FM434-UP)

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

    1. Clutch plates or clutch discs are warped.

    2. A return spring is broken or weak.

    3. A clutch solenoid modulating valve is stuck at a partial pressure.

Problem 3: There is a noise in the power train pump that is not normal.

Probable causes:

1. A loud noise at short intervals indicates foreign material in the power train system oil.

2. A constant loud noise indicates pump failure.

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

Problem 4: Noise in the transmission gearbox that is not normal

Probable causes:

1. Gears are damaged.

2. The teeth of the clutch plates are worn and/or the teeth of the clutch discs are worn. ( 554 and 574, 1FM1-433)

3. Clutch plates are slipping and the clutch discs are making noise. ( 554 and 574, 1FM1-433)

4. Other transmission components may be worn or damaged.

Problem 5: The transmission operates in FORWARD only.

Probable causes:

1. The upper proportional solenoid on the power train pump is inoperative.

2. There is a problem in the electrical circuit.

Problem 6: The transmission operates in REVERSE only.

Probable causes:

1. The lower proportional solenoid on the power train pump is inoperative.

2. There is a problem in the electrical circuit.

Problem 7: The transmission does not operate in FIRST SPEED FORWARD or in FIRST SPEED REVERSE.

Probable causes:

1. Number 1 FIRST SPEED clutch solenoid is inoperative. ( 554 or 574, 1FM1-433)

2. The SECOND SPEED clutch is not disengaged or not completely disengaged. ( 554 Forwarder)

3. There is no current to the first speed solenoid that is located on the gearshift cylinder. ( 574, 1FM434-UP)

4. There is a problem in the electrical circuit.

5. The FIRST SPEED clutch is not engaged or the FIRST SPEED clutch slips. ( 554 or 574, 1FM1-433) This may be caused by any of the following conditions:

   1. There is low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

Problem 8: The transmission does not operate in SECOND SPEED FORWARD or in SECOND SPEED REVERSE.

Probable causes:

1. Number 2 SECOND SPEED clutch solenoid is inoperative. ( 554 or 574, 1FM1-433)

2. Number 1 FIRST SPEED shift solenoid is inoperative. ( 554 Forwarder)

3. The FIRST SPEED clutch is not disengaged. ( 554 Forwarder)

4. There is a problem in the electrical circuit.

5. There is no current to the second speed solenoid that is on the gearshift cylinder. ( 574, 1FM434-UP)

6. The SECOND SPEED clutch is not engaged or the SECOND SPEED clutch slips. ( 554 or 574, 1FM1-433) This may be caused by any of the following conditions:

   1. There is low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

Problem 9: The transmission does not operate in THIRD SPEED FORWARD or in THIRD SPEED REVERSE. ( 574 1FM1-433)

Probable causes:

1. Number 3 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. There is low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

Problem 10: Clutch engagement is sudden. (This causes jerky shifting.) ( 554 or 574 1FM1-433)

Probable causes:

1. The pressure of the clutch engagement is too high.

2. Clutch solenoids are unstable.

3. A speed sensor has malfunctioned.

Problem 11: Clutch engagement is slow. (This causes slow shifting in all speeds.) ( 554 or 574 1FM1-433)

Probable causes:

1. The pressure of the clutch engagement is too low.

2. Oil pressure is low. Refer to "Problem: The transmission does not operate in any speed or the transmission slips in all speeds."

3. The pressure sensor for the drive loop is faulty.

Problem 12: Clutch engagement is slow in all FORWARD speeds, in all REVERSE speeds, or in any one speed (FORWARD and REVERSE). ( 554 or 574 1FM1-433)

Probable causes:

1. The clutch pressure is low because of leaking seals on the piston for the affected speed.

2. The clutch solenoid valve for the affected speed is contaminated.

3. The pressure sensor for the drive loop is faulty.

Problem 13: The machine does not move and the engine lugs when the transmission is engaged.

Probable causes:

1. The parking brake is not released or the parking brake may be locked up.

2. The service brakes are locked up.

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

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

5. The gears in the transmission do not turn.

   1. Too many clutches are engaged. ( 554 or 574, 1FM1-433)

   2. There is a mechanical failure in the transmission.

Problem 14: There is constant noise in the differential.

Probable causes:

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

2. The wrong type of lubricant is being used.

3. Wheel bearings are damaged or improperly adjusted.

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

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

6. There is too much backlash between the pinion and the bevel gear or too little backlash between the pinion and the bevel gear.

7. Pinion bearings are loose or worn.

8. Side bearings are loose or worn.

Problem 15: Noise occurs in the differential at different intervals.

Probable causes:

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

2. Differential bearings are loose or broken.

Problem 16: Noise only occurs during turns.

Probable causes:

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

2. The side gears are too tight in the differential case.

3. Differential pinion gears or side gears are faulty.

4. Thrust washers are damaged or worn.

5. There is too much backlash between the side gears and the pinion gears.

Problem 17: Lubricant is leaking.

Probable causes:

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

   1. The lubricant is above the proper level.

   2. The wrong type of lubricant is being used.

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

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

2. Loss of oil from the breather that is located on the differential housing. This can be caused by any of the following conditions:

   1. The oil level is too high.

   2. Hydraulic oil has filled the differential case. This can be caused by a leaking differential lock cylinder or a leaking brake cylinder.

      Note: A parking brake cylinder or a service brake cylinder could be at fault.

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

   1. The 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 on the pinion shaft is loose.

Problem 18: The drive wheels do not turn but the universal joint turns.

Probable causes:

1. An axle shaft is broken.

2. Bevel 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 19: The low oil pressure warning for charge oil pressure will not turn off.

Probable causes:

1. The charge filter is plugged.

2. The charge pressure sensor is faulty.

3. The cold start valve is faulty.

4. The charge pressure relief valve is faulty.

5. The charge pump has failed.

6. The power train pump has failed. This allows charge pump oil to drain to the tank.

7. The power train motor has failed. This allows charge pump oil to drain to the tank.

Troubleshooting Problem List (Brake System)

If repairs have been made to the brakes, be sure to purge the air from the brake system.

1. The IQAN warns the operator of a brake failure.

2. The front service brakes do not operate.

3. The rear service brakes do not operate.

4. The service brakes slip.

5. The service brakes are not applied evenly.

6. Too much force needed to push the brake pedals.

7. The parking brake does not hold the machine stationary.

8. The parking brake does not engage when the parking brake switch is deactivated.

9. The parking brake does not disengage when the parking brake switch is activated.

Probable Causes of Parking and/or Service Brake System Problems

Problem 1: The IQAN warns the operator of a brake failure.

Probable cause:

1. The pressure switch on the brake accumulator charging valve is faulty.

2. The parking brake release pressure is too low.

3. The parking brake solenoid is not receiving a signal to release.

4. The brake accumulator charging valve is faulty.

5. The implement pump has failed.

6. The precharge pressure for the brake accumulator is low.

7. The solenoid valve (cold start) is faulty.

Problem 2: The front service brakes do not operate.

Probable causes:

1. The brake within the axle housing is damaged or excessively worn.

2. The lines to the front service brakes are obstructed.

3. The precharge pressure for the brake accumulator is low.

Problem 3: The rear service brakes do not operate.

Probable causes:

1. The brake within the axle housing is damaged or excessively worn.

2. The lines to the rear service brakes are obstructed.

3. The precharge pressure for the brake accumulator is low.

Problem 4: The service brakes slip.

Probable causes:

1. One or both axles contain an incorrect hydraulic oil additive.

2. One or both axles are filled with an incorrect viscosity oil.

3. The brake disc in the axle housing is worn. Check the brake disc for excessive wear.

4. The stroke of the brake cylinder needs to be adjusted.

Problem 5: The service brakes are not applied evenly.

Probable causes:

1. The brake disc and associated components in the axle housing are excessively worn. Check the brake disc and related components for excessive wear.

2. The brake valve is sticking because of contaminated oil.

3. The service brake valve is not delivering the correct amount of pressure.

4. The stroke of the brake cylinder needs to be adjusted.

Problem 6: Too much force needed to push the brake pedal.

Probable causes:

1. The brake pedals and/or brake valves are damaged.

2. The brake valve is sticking because of contaminated oil.

Problem 7: The parking brake does not hold the machine stationary.

Probable causes:

1. The lining of brake discs are worn too much. Check the brake disc lining for excessive wear.

2. The stroke of the brake cylinder needs to be adjusted.

Problem 8: The parking brake does not engage when the parking brake switch is deactivated.

Probable causes:

1. The parking brake switch on the dash panel is faulty.

2. The solenoid on the parking brake control valve is stuck open.

3. The brake discs are excessively worn.

4. The stroke of the brake cylinder needs to be adjusted.

Problem 9: The parking brake does not disengage when the parking brake switch is activated.

Probable causes:

1. The parking brake switch on the dash panel is faulty.

2. The pressure switch for the parking brake is faulty.

3. The oil pressure from the parking brake control valve is too low.

4. The parking brake release solenoid valve is faulty.

5. Air is present in the parking brake system.