D6T Track-Type Tractor Electrohydraulic System Caterpillar

Problem List

• "The Transmission Clutch Is Engaged and the Clutch Does Not Release"

• "The Transmission Clutch Does Not Engage"

The Transmission Clutch Is Engaged and the Clutch Does Not Release

Follow this procedure if the machine seems to have a brake that is applied. Also, follow this procedure if the machine only operates in certain gears.

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Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake.

1. Check the pressures.

   1. Start the engine. Operate the engine at low idle.

   2. Push down on the service brake pedal to engage the brakes.

   3. Disengage the parking brake.

   4. Shift the transmission into the NEUTRAL position. No. 4 clutch should be the only clutch that is engaged.

   5. Shift the transmission into 0.1 FORWARD. No. 2, No. 3, and No. 6 clutch should be engaged.

   6. Measure the pressure for the clutches that do not release.

      Reference: Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Transmission Clutch Pressure - Test".

      Expected Results

      • The clutch pressures are correct.

      Results

      • OK: Stop. The clutch releases properly.

      • NOT OK: Proceed to Step 2.

2. Check the bolt torques for the transmission modulating valves.

   1. Check the torque of the bolts that hold the transmission modulating valves to the transmission control valve.

      Expected Results

      • The torque for the valves is correct.

      Results

      • OK: Proceed to Step 3.

      • NOT OK: Tighten the bolts or loosen the bolts to the proper torque. Check the operation of the machine for the original problem. If conditions are not resolved, proceed to Step 3.

3. Replace the transmission modulating valve.

   1. Replace the transmission modulating valve for the clutch that does not release.

   2. Calibrate the transmission modulating valves.

      Reference: Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Calibration" for the appropriate calibration procedure.

   3. Check the operation of the machine for the original problem.

      Expected Results

      • The original problem is resolved.

      Results

      • OK: Stop.

      • NOT OK: If the original problem is still present, the cause of the problem is uncertain. Call technical support with the information that has been gathered.

The Transmission Clutch Does Not Engage

Follow this procedure if the machine does not operate in specific gears.

1. Check the transmission main relief pressure.

   Reference: Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Relief Valve (Transmission) - Test and Adjust".

   Expected Results

   • The transmission main relief pressure is correct.

   Results

   • OK: If the original problem has not been is not resolved, proceed to Step 3.

   • NOT OK: The cause of the problem may be the adjustment of the main relief valve. The main relief valve maintains the system pressure in the control section of the power train oil pump. Proceed to Step 2.

2. Adjust the pressure setting of the main relief valve.

   Reference: Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Relief Valve (Transmission) - Test and Adjust".

   Expected Results

   • The pressure setting of the main relief valve is correct.

   Results

   • OK: The pressure setting of the main relief valve is correct. If the original problem has not been resolved, proceed to Step 3.

   • NOT OK: Proceed to Step 4.

3. Check the pressure at the clutch.

   Reference: Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Transmission Clutch Pressure - Test".

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   Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake.

   1. Start the engine. Operate the engine at low idle.

   2. Press down the service brake pedal to engage the brakes.

   3. Disengage the parking brake.

   4. Shift the transmission into a gear that requires the use of the clutch that is not functioning correctly.

   5. Measure the pressure at the clutch that does not engage.

      Expected Results

      • The hydraulic pressure is equal to main relief.

      Results

      • OK: Proceed to Step 8.

      • NOT OK: Proceed to Step 5.

4. Follow the procedure in this reference.

   Refer to “Transmission Main Relief Pressure Is Low” in this module under Troubleshooting, "Power Train System Pressure Is Low".

   Results

   • REPAIRED, OK: The original problem is resolved. Stop.

   • NOT OK: The transmission main relief pressure is correct but the problem is not resolved. Proceed to Step 5.

5. Interchange modulating valves.

   1. Interchange one of the modulating valves that should be engaged with one modulating valve that should not be engaged.

   2. Determine whether the problem follows one particular valve.

   3. Repeat the procedure for all modulating valves that affect the gear that is not functioning properly.

      Results

      • FOLLOWS: The problem follows one valve. Proceed to Step 6.

      • DOES NOT FOLLOW: Proceed to Step 7.

6. Replace the transmission modulating valve.

   1. Replace the transmission modulating valve for the clutch that does not engage.

   2. Calibrate the transmission modulating valves.

      Reference: Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Calibration" for the appropriate calibration procedure.

   3. Check the operation of the machine for the original problem.

      Expected Results

      • The original problem is resolved.

      Results

      • OK: Stop.

      • NOT OK: Proceed to Step 8.

7. Restore the modulating valve.

   1. Restore the modulating valves to the original locations. Note the suspect valve and the original location.

   2. Check the operation of the machine for the original problem.

      Expected Results

      • The original problem is resolved.

      Results

      • OK: Stop.

      • NOT OK: Proceed to Step 8.

8. Inspect the clutch.

   1. Disassemble the clutch and inspect the clutch for failure.

      Reference: Refer to Disassembly and Assembly, M0073303, "Transmission" in the Service Manual for your machine.

   2. Check for excessive wear on friction discs and clutch plates.

   3. Inspect the piston seals.

   4. Repair the components or replace the components, if necessary.

   5. Check the operation of the machine for the original problem.

      Expected Results

      • The original problem is resolved.

      Results

      • OK: Stop.

      • NOT OK: The cause of the problem is uncertain. Call technical support with the information that has been gathered. Stop.

Transmission Gear Slips

In Gear Slip Detect Feature:

Transmission slip occurs when the load on the machine exceeds the capacity of the clutch to transmit torque (torque capacity). Torque capacity depends on both the pressure at the clutch and the friction at the clutch. A deficiency in either will allow the clutch to slip when the load exceeds the torque capacity. Problems with the electrical or hydraulic systems that control the clutch can result in a pressure deficiency. Problems with the friction material, the clutch plates, or even the wrong oil type, may result in a friction deficiency.

While the transmission is in gear, the Gear Slip Detect Feature continuously monitors the torque converter and transmission output speeds, to determine whether the transmission is slipping. When slippage in a particular gear is detected, the Transmission ECM limits the engine torque to prevent more slip and protect the transmission.

If limiting engine torque does not stop the transmission clutch slip, then the Transmission ECM will lock out the problem gear. The ECM also activates an event code to help in troubleshooting the problem. Refer to Event Codes in this manual for a list of applicable event codes related to the Slip Detect Feature. Restarting the machine clears the active event code and allows temporary operation. Only light-duty activities should be attempted. The lock-out will reoccur if a transmission gear slip is detected again.

Transmission speed sensor diagnostics and transmission slip events are interrelated. The "In Gear Slip Detect" feature detects clutch slip as long as the torque converter and the transmission output speed sensors are working properly. If there are problems with these sensors, this feature can falsely detect slip. Follow the Speed Sensor Troubleshooting before the Transmission Slip Troubleshooting procedure whenever transmission slip events and both speed sensor diagnostics are active at the same time

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Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake.

Illustration 1	g06185985

Illustration 2	g06182623

Torque Converter Lockup Clutch Not Available

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Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake.

Illustration 3	g06186001

Torque Converter Lockup Clutch Slips

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Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake.

Illustration 4	g06182676

Illustration 5	g06182688