D8T and D9T Track-Type Tractors Caterpillar

Problem List

• "The Machine Does Not Move or the Machine Moves Slowly"

The Machine Does Not Move or the Machine Moves Slowly

Follow this procedure if the machine does not move or if the machine moves slowly.

Initially, make sure that the symptom is active. If the symptom is intermittent, then a probable cause is oil contamination.

Next, a check of the brake pressure guides the diagnosis of the problem to the brake system or to the transmission and torque converter.

If the brake pressure is correct, then the brake system and the power train system pressure are eliminated as the probable cause of the problem since sufficient pressure is sent to the brake to release the brake. Therefore, the engagement of the torque converter stator clutch or the transmission clutches is the probable cause.

If the brake pressure is not correct, then a check of the system pressure determines if the main relief valve or the brake valve is the probable cause. The system pressure allows the brake control valve to supply sufficient pressure to the brakes.

If the system pressure is correct, then inspect the brake valve.

1. Check for the symptom.

   1. Determine that the symptom is active.

   2. Complete this procedure only if the symptom is active.

      Results

      • ACTIVE: Proceed to Step 2.

      • NOT ACTIVE: If the symptom is not active, oil contamination could be the problem. Change the power train oil. Change the oil filter element and clean the screens. Stop.

2. Check the brake pressure.

   The brakes are engaged by spring force. The brakes are released by pressure oil which is sent from the brake control valve to the brakes. Therefore, insufficient pressure oil to the brakes is a probable cause of the symptom.

   Reference: Refer to (D9T) Specifications, Systems Operation Testing and Adjusting, KENR8943, "Brake Pressure - Test".

   Expected Results

   • The pressure is correct.

   Results

   • OKAY: Proceed to Step 3.

   • NOT OKAY: Proceed to Step 6.

3. Check torque converter stator clutch engagement

   The stator clutch in the torque converter is applied with power train oil pressure by the stator clutch control valve. Insufficient oil pressure at the clutch is a probable cause of the symptom.

   Reference: Refer to (D9T) Specifications, Systems Operation Testing and Adjusting, KENR8943, "Stator Clutch Pressure – Test".

   Reference: Refer to (D9T) Specifications, Systems Operation Testing and Adjusting, KENR8943, "Brake Pressure - Test".Refer to “Stator Clutch does not Engage” in this module under Troubleshooting, “Torque Converter

   Expected Results

   • The stator clutch engages.

   Results

   • OKAY: Proceed to Step 5.

   • NOT OKAY: Proceed to Step 4.

4. Check the torque converter stator clutch

   1. Inspect the torque converter stator clutch valve to see if the valve moves as intended

   2. Disassemble the torque converter.

   3. Check for leaking seals or damaged clutch components

   4. Replace any damaged components as necessary.

      Expected Results

      • The original problem is resolved.

      Results

      • OKAY: Stop.

      • NOT OKAY: The cause of the problem is uncertain. Call technical support with the information that has been gathered.
   Show/hide table

   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.

5. Check for transmission drag.

   1. Place pressure gauges on all transmission clutches.

   2. Operate the engine.

   3. Disengage the parking brake.

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

   5. Shift through all the transmission gears.

   6. Check that the proper clutches engage for each gear.

   7. Check that the clutches disengage properly for each gear. The clutch that is disengaged should have a pressure below 137 kPa (20 psi).

      Expected Results

      • The transmission clutches engage and the transmission clutches disengage properly.

      Results

      • OKAY: The engagement of the transmission clutches was eliminated as the source of the problem. Since the torque converter stator clutch pressure was correct, torque converter stator clutch was eliminated as the source of the problem. Since the brake pressure was correct, then the brake control valve was eliminated as the source of the problem. Therefore, the brake is the probable cause of the problem. Proceed to Step 7.

      • THE CLUTCH DOES NOT ENGAGE: Proceed to Step 8.

      • THE CLUTCH DOES NOT DISENGAGE: Proceed to Step 9.

6. Check the system pressure.

   Reference: Refer to (D9T) Specifications, Systems Operation Testing and Adjusting, KENR8943, "Relief Valve (Transmission) - Test and Adjust".

   Expected Results

   • The system pressure is correct.

   Results

   • OKAY: The brake pressure is not correct. The system pressure is correct. Next, inspect the brake control valve. Proceed to Step 11.

   • NOT OKAY: 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 10.

7. Check the brakes.

   The brake pressure is correct and the engagement of the transmission clutches is correct. Therefore, the brakes are the probable cause of the problem.

   1. Disassemble the brakes.

   2. Check these components of the brakes for failure: seals, splines, friction discs, and brake plates.

   3. Replace any damaged components, if necessary.

   4. Calibrate the brakes.

      Expected Results

      • The original problem is resolved.

      Results

      • OKAY: Stop.

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

8. Follow the procedure in this reference.

   Refer to “The Transmission Clutch Does Not Engage” in this module under Troubleshooting, "Transmission Clutch".

   Results

   • REPAIRED OKAY: Stop.

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

9. Follow the procedure in this reference.

   Refer to “The Transmission Clutch Is Engaged And The Clutch Does Not Release” in this module under Troubleshooting, "Transmission Clutch".

   Results

   • REPAIRED OKAY: Stop.

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

10. Follow the procedure in this reference.

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

    Results

    • REPAIRED OKAY: Stop.

    • NOT OKAY: Proceed to Step 11.

11. Manually inspect the brake control valve.

    1. Disassemble the brake control valve and inspect the valve for damage.

    2. Repair the components and/or replace the components, if necessary.

    3. Calibrate the brakes.

       Expected Results

       • The original problem is resolved.

       Results

       • OKAY: Stop.

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