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

Illustration 1	g02709913
The 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 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) Torque converter inlet pressure tap 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

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

• The transmission overheats.

• Pump noise that is not heard normally.

• Noise in the transmission that is not normal

• The transmission operates in FORWARD only.

• The transmission operates in REVERSE only.

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

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

• The transmission does not operate in THIRD SPEED FORWARD or in 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 causing jerky shifting.)

• Clutch engagement is slow causing 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 machine does not move and engine speed lugs when the transmission is engaged.

• 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.

Troubleshooting

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

Check for any service codes that may have been generated before troubleshooting a problem. Use the built-in electrical diagnostics that are performed with the Advisor Monitoring and 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 in order to detect faults in the electronic system for the power train. For additional information on the operation and troubleshooting of the power train electronic control module (ECM), refer to the Service Manual module for Systems Operation, Testing and Adjusting Power Train System.

ReferenceFor additional information on troubleshooting the power train electronic control module (ECM), refer to Service Manual, UENR2421, "992K Wheel Loader and 854K Wheel Dozer Monitoring System" for diagnostic procedures.

Probable Causes of Transmission Problems

The transmission does not operate in any gear or the transmission slips in all gears.

1. The fuse for the power train control is missing or broken.

2. There is a problem in the electrical circuit.

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

   1. The oil level is low.

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

   3. Oil pump failure.

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

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

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

4. There is a torque converter failure.

5. There is a mechanical failure in the transmission.

6. Clutch discs and clutch plates are excessively worn.

7. The torque converter impeller clutch is not engaged or the impeller clutch is slipping.

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. Clutch slip may be caused by any of the following conditions:

   1. Low oil pressure. Refer to 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. Low oil flow may be caused by pump wear or by leakage in the transmission hydraulic system.

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

10. The magnetic screen for the pump inlet is plugged.

11. The torque converter inlet ratio valve (11) is stuck open causing low oil flow through the torque converter.

12. The clutch or clutches are not fully released. This condition is called clutch drag and may be caused by any of the following conditions:

    1. There are warped plates or warped discs.

    2. A return spring is broken or weak.

Pump noise that is not heard normally.

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.

Noise in the transmission that is not normal

Probable causes

1. Transmission components are worn or damaged.

   1. Gears are damaged.

   2. The teeth of the clutch plates and/or clutch discs are worn.

   3. The clutch plates are slipping or noise from the clutch discs.

   4. There are other transmission components that are worn or damaged.

The transmission operates in FORWARD only.

Probable causes

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

2. There is a problem in the electrical circuit.

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

   1. Low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

4. Selector spool (14) is stuck.

The transmission operates in REVERSE only.

Probable causes

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

2. There is a problem in the electrical circuit.

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

   1. Low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

4. Selector spool (14) is stuck.

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

Probable causes

1. Number 5 clutch solenoid (5) 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 problem may be caused by any of the following conditions:

   1. Low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

4. Selector spool (18) is stuck.

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

Probable causes

1. Number 4 clutch solenoid (6) 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 problem may be caused by any of the following conditions:

   1. Low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

4. Selector spool (22) is stuck.

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

Probable causes

1. Number 3 clutch solenoid (2) 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 problem may be caused by any of the following conditions:

   1. Low oil pressure due to leaking piston seals.

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

   3. Clutch components are broken.

4. Selector spool (18) is stuck.

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 (13) is stuck.

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

3. Springs of load piston (20) are weak or damaged. Springs or spacers are missing.

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

Probable causes

There is too much leakage in the piston seals of the REVERSE clutch.

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

Probable causes

There is too much leakage in the piston seals of the FORWARD clutch.

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 (13) is sticking.

2. Load piston (20) is stuck.

3. The wrong load piston springs or too many spacers are being used.

4. Slug (12) is worn. The bore for the modulating relief valve (13) is worn.

The pressure differential between P1 and P2 is not correct.

Probable causes

Pressure differential valve (19) is not operating correctly because of a spring that is weak or damaged. Also, the wrong spring may be installed.

Clutch engagement is sudden causing jerky shifting.

Probable causes

1. Pressure differential valve (19) is not operating correctly because of a spring that is weak or damaged. Also, the wrong spring may be installed.

2. Load piston (20) is stuck.

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

Clutch engagement is slow causing slow shifting in all gears.

Probable causes

1. The screen orifice for the load piston is dirty or plugged.

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

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

4. Modulating relief valve (13) is stuck.

5. The impeller clutch solenoid valve (9) has malfunctioned.

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 for the affected gear.

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

Probable causes

1. 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 or too many clutches are engaged.

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

There is a problem in the electrical circuit.

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

Probable causes

1. The backup alarm fuse has failed.

2. The backup alarm has failed.

3. There is a problem in the electrical circuit.

Stall speed is low.

Probable causes

1. Engine performance is not correct.

2. The oil is cold.

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.

5. The torque converter impeller clutch is slipping.

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.