725, 730 and 730 EJECTOR Articulated Trucks Power Train Caterpillar

Note: The troubleshooting information is intended to aid in diagnosing a given problem. The possible causes are ordered from the most probable cause to the least probable cause. The possible causes should be examined in order until the problem is resolved.

Refer to Systems Operation, Testing and Adjusting, "Machine Preparation for Troubleshooting" before you perform any testing and adjusting or troubleshooting.

Prior to carrying out troubleshooting on the torque converter, use Caterpillar ET in order to diagnose any fault codes that may be present. Refer to Systems Operation, Troubleshooting,Testing and Adjusting, RENR8035, "Power Train Electronic Control System".

If fault codes are present, repair the cause of the fault code.

The Torque Converter Is Overheating

Possible Cause

1. The machine may have been operated incorrectly.
   • Operate the machine in the correct manner. Refer to Operation and Maintenance Manual, SEBU7814.

2. The temperature sensors in the transmission hydraulic control system may not be functioning correctly.
   • Use ET in order to determine whether there are any faults with the temperature sensors.

3. The level of the engine coolant is lower than the specification.
   • Check the engine coolant level. Refer to Systems Operation, Testing and Adjusting, "Visual Inspection".

4. The power train oil level is lower than the specification.
   • Check the power train oil level. Refer to Systems Operation, Testing and Adjusting, "Visual Inspection".

5. The engine cooling system and the fan drive system may not be functioning correctly.
   • Refer to Systems Operation, Testing and Adjusting, RENR6725, "Machine Systems" for further information regarding the fan drive system.

   • Refer to Systems Operation, Testing and Adjusting, SENR9888 for further information on the engine.

6. There is debris and damaged components in the power train.
   • Inspect the oil filter for debris.

   • Determine the origin of the debris and repair the damaged component.

   • Change the oil in the power train and install a new oil filter.

7. The coolant flow through the transmission oil cooler is below the specification.

8. The oil flow through the transmission oil cooler is below the specification.
   • Check the oil pressure to the transmission oil cooler. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures".

9. The torque converter inlet pressure is outside specifications.
   • Check the torque converter inlet pressure. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures".

   • Adjust the transmission hydraulic control relief valve. Refer to Systems Operation, Testing and Adjusting, "Transmission Oil Supply".

10. The torque converter outlet pressure is outside specifications.
    • Check the torque converter outlet pressure. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures".

    • Refer to Systems Operation, Testing and Adjusting, "Transmission Oil Supply".

11. The torque converter is worn or damaged.
    • Inspect the components of the torque converter for wear or damage. Refer to Disassembly and Assembly, RENR3448, "Torque Converter - Disassemble and Assemble".

The Torque Converter Lockup Clutch Does Not Disengage And The Engine Dies At Low Speed

Possible Cause

1. The wiring harness for the power train may be damaged.
   • Check the wiring and check the connectors for damage. Refer to Systems Operation, Testing and Adjusting, "Visual Inspection".

   • Repair any damage that is found in the wiring harness or replace any loose connections that are found.

2. There is debris and damaged components in the power train.
   • Inspect the oil filter for debris. Refer to Systems Operation, Testing and Adjusting, "Visual Inspection".

   • Determine the origin of the debris and repair the damaged component.

   • Change the oil in the power train and install a new oil filter.

3. The solenoid on the modulating valve (torque converter lockup clutch) does not function correctly.
   • Check the operation of the solenoid before the engine start switch is turned off. Refer to Systems Operation, Testing and Adjusting, "Modulating Valve (Torque Converter Lockup Clutch) - Test".

4. The shuttle valve in the modulating valve (torque converter lockup clutch) may be sticking.
   • Check the operation of the modulating valve (torque converter lockup clutch). Systems Operation, Testing and Adjusting, "Modulating Valve (Torque Converter Lockup Clutch) - Test".

5. The piston in the torque converter lockup clutch may be sticking.
   • Check the oil pressure in the torque converter lockup clutch. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures - Test".

   • Check the condition of the piston in the torque converter lockup clutch. Refer to Disassembly and Assembly, RENR3448, "Torque Converter - Disassemble and Assemble".

The Torque Converter Lockup Clutch Does Not Engage

Possible Cause

1. The wiring harness for the power train may be damaged.
   • Check the wiring and check the connectors for damage. Refer to Systems Operation, Testing and Adjusting, "Visual Inspection".

   • Repair any damage that is found in the wiring harness or replace any loose connections that are found.

2. The power train oil level is below the specification.
   • Check the power train oil level. Refer to Systems Operation, Testing and Adjusting, "Visual Inspection".

3. There is debris and damaged components in the power train.
   • Inspect the oil filter for debris.

   • Determine the origin of the debris and repair the damaged component.

   • Change the oil in the power train and install a new oil filter.

4. The pressure of the oil in the transmission hydraulic control system may not be within the specification.
   • Test the pressures of the oil in the transmission hydraulic control system. Make any necessary repairs or adjustments. Refer to Systems Operation, Testing and Adjusting, "Transmission Oil Supply".

5. The solenoid on the modulating valve (torque converter lockup clutch) does not function correctly.
   • Check the operation of the solenoid before the engine start switch is turned off. Refer to Systems Operation, Testing and Adjusting, "Modulating Valve (Torque Converter Lockup Clutch) - Test".

6. The shuttle valve in the modulating valve (torque converter lockup clutch) may be sticking.
   • Check the operation of the modulating valve (torque converter lockup clutch). Systems Operation, Testing and Adjusting, "Modulating Valve (Torque Converter Lockup Clutch) - Test".

7. The components in the torque converter lockup clutch may be worn.
   • Check the oil pressure in the torque converter lockup clutch. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures - Test".

   • Check the condition of the piston in the torque converter lockup clutch. Refer to Disassembly and Assembly, "Torque Converter - Disassemble and Assemble".

The Machine Will Not Move With A Full Load

Possible Cause

1. There is a fault with the freewheel clutch in the torque converter or the freewheel clutch is incorrectly assembled.
   • Check that the freewheel clutch is correctly installed.