D6N Track-Type Tractor Power Train Caterpillar

Use this section in order to locate problems in the power train. Also, use this section in order to correct problems in the power train.

Initial Troubleshooting

Many problems will produce symptoms which will be detected by the monitoring system. These symptoms will also be logged by the monitoring system. Begin your diagnosis of the problem by consulting the Service Manual, "Power Train Electronic Control System" for your machine.

First, always make a visual check. Then, check the operation of the machine and the operation of the instruments.

Visual Checks

1. Check the power train oil level.

2. Check the oil level in the final drives.

3. Check all oil lines, all hoses, and all hose connections for leaks and for damage. Look for oil on the ground under the machine.

4. Check the electrical wiring for the transmission and the steering and brake control valve.

5. Check the adjustment of the track.

6. Check the screens in the bevel gear case and in the torque converter housing for foreign material. Check the filter element for foreign material.

   1. Bronze colored particles are an indication of a clutch failure.

   2. Shiny steel particles are an indication of a pump failure.

   3. Rubber particles are an indication of a seal failure or a hose failure.

   4. Aluminum particles are an indication of a torque converter failure.

If you find metal or rubber particles, all components of the power train oil system must be cleaned out. Always replace damaged parts with new parts.

Checks During Operation

Show/hide table

To prevent personal injury when checks are made while the machine is in operation, make sure only approved personnel are on the machine. Keep other personnel off the machine and in view of the operator. Make sure checks are done in an open area.

Operate the machine in each direction and at all speeds. Take note of all noises that are not normal. Locate the source of those noises. When the operation of the machine is not correct, refer to the List of Checks During Operation. This section lists problems and probable causes.

List of Checks During Operation

Transmission

Problem

The transmission does not operate in any speed. The transmission does not engage in all speeds or there is clutch slippage.

Probable Cause

1. Low oil pressure in the system. Low oil pressure can be caused by one of the following problems.

   1. Low oil level

   2. Failure of the transmission oil pump or the pump drive

   3. Air leakage on the inlet side of the transmission oil pump

   4. Oil leakage inside the transmission

   5. Incorrect main relief valve adjustment

   6. Main relief valve that is not closing

   7. Modulating valve for the No. 4 clutch which is installed backward

   8. Electrical problem

2. Mechanical failure in the transmission

3. Failure of the torque converter

4. Failure of the transfer and bevel gears

5. Failure in the final drives

Problem

The transmission does not make a shift.

Probable Cause

1. Low oil level

2. Low clutch pressure

3. Electrical problem

Problem

Slow shifting.

Probable Cause

1. Low oil pressure

2. Air leaks on the inlet side of the transmission oil pump

Problem

The transmission engages very suddenly. This sudden engagement causes rough shifting.

1. Valve springs that are weak or damaged

2. Modulating valves for the transmission are not calibrated. Refer to the Service Manual, "Power Train Electronic Control System" for your machine.

Problem

The transmission operates in FORWARD speeds only.

Probable Cause

1. No. 1 clutch is not engaged or the clutch slips. This can be caused by one of the following problems.

   1. Low oil pressure

   2. Oil leakage

   3. Excessive wear on the discs and plates

   4. Broken parts in the clutch

   5. Malfunctioning of one of the modulating valves for the transmission

   6. Electrical problem

Problem

The transmission operates in REVERSE speeds only.

Probable Cause

1. No. 2 clutch is not engaged or the clutch slips. This can be caused by one of the following problems.

   1. Low oil pressure

   2. Oil leakage

   3. Excessive wear on the discs and plates

   4. Broken parts in the clutch

   5. Malfunctioning of one of the modulating valves for the transmission

   6. Electrical problem

Problem

The transmission will not operate in FIRST speed FORWARD or in FIRST speed REVERSE.

Probable Cause

1. The No. 5 clutch is not engaged or the clutch is slipping. This can be caused by one of the following problems.

   1. Low oil pressure

   2. Oil leakage

   3. Excessive wear on the discs and plates

   4. Broken parts in the clutch

   5. Malfunctioning of one of the modulating valves for the transmission

2. The modulating valve for the No. 3 clutch or the No. 4 clutch is not functioning properly. Two speed clutches are engaged simultaneously.

Problem

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

Probable Cause

1. The No. 4 clutch is not engaged or the clutch is slipping. This can be caused by one of the following problems.

   1. Low oil pressure

   2. Oil leakage

   3. Excessive wear on the discs and plates

   4. Broken parts in the clutch

   5. Malfunctioning of one of the modulating valves for the transmission

2. The modulating valve for the No. 3 clutch or the No. 5 clutch is not functioning properly. Two speed clutches are simultaneously engaged.

Problem

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

Probable Cause

1. The No. 3 clutch is not engaged or the clutch is slipping. This can be caused by one of the following problems.

   1. Low oil pressure

   2. Oil leakage

   3. Excessive wear on the discs and plates

   4. Broken parts in the clutch

   5. Malfunctioning of one of the modulating valves for the transmission

2. The modulating valve for the No. 4 clutch or the No. 5 clutch is not functioning properly. Two speed clutches are simultaneously engaged.

Problem

The transmission does not disengage when the direction lever is in NEUTRAL.

Probable Cause

1. A direction clutch is engaged. The clutch will not release because there is an electrical problem or a mechanical problem with one of the modulating valves on the transmission.

Problem

The transmission engages but the machine will not move.

Probable Cause

1. Failure of the final drives

2. Failure of the transfer and bevel gears

3. The gears in the transmission will not move. This may be caused by one of the following problems.

   1. Too many clutches are engaged.

   2. Mechanical failure in the transmission

4. Mechanical failure in the torque converter

5. Brakes are not releasing. This may be caused by the following problem.

   1. Low pressure in the power train oil system

Problem

The transmission gets hot.

Probable Cause

1. Low oil level

2. High oil level

3. Cores in the oil cooler that are not completely open

4. Low oil flow because of wear in the transmission oil pump

5. Long periods of operation with the torque converter at stall speed or near stall speed

6. Too much resistance between the clutch plates and the discs

   Note: This resistance exists despite the disengagement of the clutches.

Problem

There is abnormal noise in the transmission oil pump.

Probable Cause

1. Loud sounds at short intervals that indicate particles are going through the pump. These noises can be caused by pump cavitation.

2. Constant loud noises can indicate pump failure.

3. Air leakage at the inlet side of the pump can cause abnormal noises.

Torque Converter

The information that follows can be used to diagnose problems in the torque converter. This information does not list every possible problem. The problem could be in the engine or the transmission.

Problem

The torque converter gets hot.

Probable Cause

1. Bad temperature gauge or sending unit

2. Long periods of operation with the torque converter at stall speed or near stall speed

3. Abnormal cooling system operation

   1. Cores in the oil cooler that are not completely open

   2. Restriction in the oil cooler lines

4. Low oil pressure

   1. Low oil level

   2. Torque converter inlet relief valve that is not operating correctly

   3. Torque converter outlet relief valve that is not closing

   4. Leakage around seals in the torque converter

5. Air in the oil system

6. Torque converter scavenge line that is restricted or plugged

   1. Screen in the torque converter housing that is plugged

7. Mechanical failure in the torque converter

Problem

The torque converter inlet pressure is high.

Probable Cause

1. Torque converter inlet relief valve that is not operating correctly

2. Restrictions in the torque converter outlet relief valve

3. Restrictions in the outlet line to the oil cooler

4. Power train oil that is not at normal operating temperature

Problem

The torque converter inlet pressure is low.

Probable Cause

1. Inadequate flow from the transmission oil pump

2. Torque converter inlet relief valve

   1. Dirt or foreign material in the valve

3. Torque converter outlet relief valve

   1. Weak spring

   2. Dirt or foreign material in the valve

4. Seal leakage in the torque converter

Note: Dirt and/or foreign material in the valves will prevent the valves from closing properly.

Problem

There are noises in the torque converter that have the sound of metal to metal contact.

Probable Cause

1. Bearings with excessive wear or damage

2. Loose turbine, impeller, or stator blades

3. Too much side load on the output shaft

Service Brakes

Problem

The service brakes will not engage.

Probable Cause

1. Electrical problem

2. Contamination in the brake pilot valve

3. Brake spool that is hanging up

4. Excessive wear or damage to the brake plates or discs

5. Broken belleville springs

Problem

Both brakes will not release.

Probable Cause

1. Electrical problem

2. Contamination in both brake pilot valves

3. Leaking seals on the brake pistons

4. Poppet assembly for the solenoid on the brake valve that is stuck open

5. Low pressure in the power train oil system