966H, 972H and 980H Wheel Loaders Power Train Electronic Control System Caterpillar

Illustration 1	g00908031
Schematic for the Transmission Hydraulic System (1) Transmission hydraulic control relief valve (2) Torque converter (3) Torque converter outlet relief valve (if equipped) (4) Transmission oil filter (5) Modulating valve (transmission clutch) for the Number 1 clutch (6) Modulating valve (transmission clutch) for the Number 4 clutch (7) Modulating valve (transmission clutch) for the Number 2 clutch (8) Modulating valve (transmission clutch) for the Number 5 clutch (9) Modulating valve (transmission clutch) for the Number 3 clutch (10) Modulating valve (transmission clutch) for the Number 6 clutch (11) Transmission oil pump (12) Torque converter inlet relief valve (13) Suction screen and magnet (14) Oil sump (15) Transmission lubrication (16) Oil cooler (A) Pump pressure tap at the transmission hydraulic control relief valve (B) P3 Torque converter inlet pressure tap (C) Torque converter outlet pressure tap (D) Sampling valve for the transmission oil (G) Pressure tap for the Number 1 clutch (H) Pressure tap for the Number 4 clutch (J) Pressure tap for the Number 2 clutch (K) Pressure tap for the Number 5 clutch (L) Pressure tap for the Number 3 clutch (M) Pressure tap for the Number 6 clutch (N) 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

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.

Make sure that you check for any service codes that have been generated before troubleshooting a problem.

ReferenceFor more information on checking for service codes with the Caterpillar Monitoring System, refer to Testing and Adjusting, "Using Caterpillar Monitoring System to Determine Service Codes".

ReferenceFor more information on checking for service codes with the Caterpillar Electronic Technician (ET), refer to Testing and Adjusting, "Using Caterpillar Electronic Technician (ET) to Determine Service Codes".

ReferenceFor additional information about troubleshooting service codes, refer to Testing and Adjusting, "Troubleshooting Service Codes".

Troubleshooting Problem List

• 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 low.

• Torque converter pressure is high.

• The torque converter overheats.

Troubleshooting

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

ReferenceFor additional information about troubleshooting the power train electronic control module (ECM), refer to Testing and Adjusting, "Troubleshooting Service Codes".

Probable Causes of Power Train Problems

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. The 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. Torque converter inlet relief valve (12) is bypassing too much oil flow.

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

Problem: The lubrication pressure is high.

Probable causes:

There is a restriction in an oil passage inside the transmission.

Problem: The torque converter pressure is low.

Probable causes:

1. Torque converter inlet relief valve (12) is bypassing too much oil flow.

2. Adjustment of torque converter outlet relief valve (3) (if equipped) is not correct.

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

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

Problem: The 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 relief valve (12) is stuck in the closed position.

4. The oil is not at normal operating temperature.

Problem: 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. The 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 too high or too low.

4. The coolant level in the radiator is low.

5. The oil cooler or oil lines are restricted.

6. The oil flow through the torque converter is too low. This may be caused by any of the following conditions:

   1. Torque converter inlet relief valve (12) is bypassing too much oil flow.

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