854K Wheel Dozer and 992K Wheel Loader Power Train Caterpillar

Illustration 1	g02709913
Schematic for the transmission hydraulic control (1) Number 2 clutch solenoid (2) Number 3 clutch solenoid (3) Priority valve (4) Number 1 clutch solenoid (5) Number 5 clutch solenoid (6) Number 4 clutch solenoid (7) Flow control orifice (8) Lockup clutch solenoid valve (if equipped) (9) Impeller clutch solenoid valve (10) Slug (11) Torque converter inlet ratio valve (12) Slug (13) Modulating relief valve (14) Direction selection spool (15) Torque converter (16) Lockup clutch (if equipped) (17) Impeller clutch (18) Selector spool for first speed and for third speed (19) Pressure differential valve (20) Load piston (21) Flow control orifice (22) Selector spool for second speed (23) Transmission oil filter (25) Flow control orifice (26) Oil pump (27) Torque converter outlet relief valve (28) Oil cooler (29) Magnetic Screen (30) Lubrication passage for transmission (31) Reservoir (32) Reservoir (A) Oil pump output pressure tap (B) Pump pressure tap (C) Pressure tap for lockup clutch (if equipped) (D) Pressure tap for the torque converter P3 (E) Speed clutch pressure tap P1 (F) Pressure tap for impeller clutch (G) Direction clutch pressure tap P2 (H) Pump pressure tap (I) Torque converter outlet pressure tap (J) Transmission lubrication pressure tap

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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.

Operational Checks

Note: 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

• Torque converter pressure is high.

• Torque converter pressure is low.

• The torque converter overheats.

• The torque converter does not respond correctly to the left service brake pedal.

• The lockup clutch does not engage.

• The lockup clutch engages intermittently.

• The impeller clutch does not engage.

Troubleshooting

Note: In the following section, when components are referenced with a number, refer to the schematic in 1.

Use the built-in electrical diagnostics that are performed with the Advisor Monitoring Systemand with the electronic control module in order to determine the service codes for the power train electronic control module.

Note: This machine is equipped with a power train electronic control. The power train electronic control has built-in system diagnostics that detect faults in the electronic system of the power train.

ReferenceFor additional information on the operation of the power train electronic control module (ECM) and troubleshooting the power train ECM, refer to the Service Manual module for Systems Operation, Testing and Adjusting for the machine that is being serviced.

ReferenceFor additional information on troubleshooting the power train electronic control module (ECM), refer to the Service Manual Module Systems Operation, Testing and Adjusting, UENR2421, "992K Wheel Loader and 854K Wheel Dozer Monitoring System"

Probable Causes of Problems in the Torque Converter

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.

3. Torque converter inlet ratio valve (11) is stuck in the closed position.

Torque converter pressure is low

Probable causes

1. Torque converter inlet ratio valve (11) is stuck in the open position.

2. Adjustment of torque converter outlet relief valve (27) is not correct.

3. The valve spool in torque converter outlet relief valve (27) does not move.

4. Pump flow or oil pressure is low. Low pump flow or low oil pressure 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. Oil pump failure.

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

   5. Leakage inside the transmission (worn seals around the clutch piston)

   6. Modulating relief valve (13) is stuck open.

The torque converter overheats

Probable causes

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

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 transfer gear case 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 too low. Low oil flow through the torque converter may be caused by any of the following conditions:

   1. The torque converter inlet ratio valve (11) is bypassing too much oil flow.

   2. Pump flow or oil pressure is low. Refer to the Problem: Torque converter pressure is low.

The torque converter does not respond correctly to the left service brake pedal

Probable causes

1. Minimum Impeller clutch dump pressure calibrated too high, use ET to reduce the minimum dump pressure setting (if applicable).

2. Ensure most recent Powertrain Software is installed.

3. The torque converter is in the mode for reduced rimpull (if equipped). This changes the response of the left service brake pedal.

4. The sensor for the left service brake pedal is calibrated incorrectly.

5. The left service brake pedal position sensor is faulty.

6. The impeller clutch solenoid or the impeller clutch solenoid valve is faulty.

7. There is a problem in the electrical circuit.

Detailed Troubleshooting

1. Check Impeller Clutch Pressure with the left pedal depressed and not depressed at high idle.

   Expected Result: As the left pedal is pressed, pressure from ICTC valve to impeller clutch should decrease.

2. Make sure that brake pressures are correct.

3. Reduce minimum dump pressure setting in Cat ET (if available).

   Note: Do not set dump pressure too low. This can cause issues with impeller clutch recovery response. Contact DSN for more information.

4. Check pedal position sensor. Make sure that duty cycle is changing in Cat ET as pedal is depressed/released. Refer to Service Magazine, SEPD1464 for more information.

5. Update to most current Software and run left pedal and Impeller Clutch Calibrations, if necessary reduce minimum dump pressure setting in Cat ET.

   Note: Do not set dump pressure too low. This can cause issues with impeller clutch recovery response. Contact DSN for more information.

6. Check stability of Torque Converter (TC) Output Speed sensor at low idle and high idle. Torque Converter Output speed will be ±50 RPM of engine RPM. Operate the machine at a steady state in forward direction, if you get a negative speed during this test, replace the speed sensor. Finally, complete a third gear stall test, if a TC output speed signal is detected, troubleshoot the speed sensors. Refer to Service Magazine, SEPD1389 for correct speed sensor and wiring on older machines.

7. Unplug positive and negative wires at ECM for Impeller Clutch Solenoid, check resistance in circuit.

   Resistance will vary based on temperature, see the note below.

   • Nominal at 25° C (77° F) : 7.75 ±3 Ohms

   • Nominal at -40° C (-40° F) : 5.81 ± 3 Ohms

   • Nominal at 121° C (250° F) : 12.15 ±3 Ohms.

   Expected results: Resistance values should be ±3 ohms from the previously described nominal set points.

   • If resistance values are higher than expected. Inspect harness for corroded pins.

   • Inspect resistance values at Impeller clutch solenoid connector.

   • If resistance is lower than expected. Inspect harness shorts to ground.

8. If all of the previous checks and calibrations have been implemented and problem still persists. Change the ICTC valve for Impeller Clutch.

9. Contact DSN for further assistance to determine if component removal is required.

The lockup clutch does not engage

Probable causes

1. The lock up clutch solenoid is not calibrated.

2. The torque converter pedal sensor is not calibrated or is faulty.

3. The transmission input speed sensor is faulty.

4. The transmission is in first gear forward.

5. The transmission is 1st/2nd gear reverse or second gear forward and the on/off switch for the lock up clutch is OFF.

6. The lockup clutch solenoid or the lockup clutch solenoid valve is faulty.

7. There is a problem in the electrical circuit.

The lockup clutch engages intermittently.

Probable causes

1. Erratic signals from the engine speed sensor or the transmission input speed sensor can cause the lockup clutch in the torque converter to cycle on and off when the lockup clutch is enabled.

2. The torque converter pedal sensor is calibrated incorrectly.

The impeller clutch does not engage

Probable causes

1. The impeller clutch solenoid or the impeller clutch solenoid valve is faulty.

2. There is a problem in the electrical circuit.