D6T Track-Type Tractor Electrohydraulic System Caterpillar

Transmission Controls

Illustration 1	g06123406
D6T View From the Top Side of the Transmission (1) Modulation Valve (No. 1 Clutch for Reverse Direction) (2) Modulation Valve (No. 2 Clutch for Forward Direction) (3) Modulation Valve (No. 3 Clutch) (4) Modulation Valve (No. 4 Clutch) (5) Modulation Valve (No. 5 Clutch) (6) Modulation Valve (No. 6 Clutch) (7) Transmission Relief Valve

Problem List

• "The Transmission Does Not Operate in Any Gear"

• "Harsh Shifting"

• "The Machine Makes an Abrupt Stop When You Shift into the NEUTRAL Position"

• "The Transmission Does Not Change Speeds but the Machine Moves"

• "The Transmission Operates in FORWARD Speeds Only"

• "The Transmission Operates in REVERSE Speeds Only"

• "The Transmission Does Not Operate in Specific Speeds"

The Transmission Does Not Operate in Any Gear

1. Use The Message Display In Order To Check The FNR Signal From The Direction Control.

   1. Press the menu button.

   2. Arrow down to "Machine Status".

   3. Select "Powertrain" from the menu displayed.

   4. Look for the following parameters:

      • "DirSelPosSnsr#1"

      • "DirSelPosSnsr#2"

   5. These parameters should correspond to the values in Table 2.

      Expected Results

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      Table 2

      FORWARD	85 ± 5%
      NEUTRAL	50 ± 10%
      REVERSE	13 ± 7%

      Results

      • OK: The direction control is within tolerance. Proceed to Step 2.

      • NOT OK: Contact the technical communicator for your Dealer for possible consultation with Caterpillar.

2. Operate The Machine.

   The two primary causes of this symptom are the transmission and the brakes. This step guides the diagnosis of the problem to the brakes or to the transmission.

   1. Start the engine.

   2. Operate the engine at high idle.

   3. Attempt to operate the machine. Shift the transmission into third gear forward. Observe the engine speed during shifts.

      Expected Results

      • The engine speed decreases. The engine is near stall condition during shifts.

      Results

      • NEAR STALL: Proceed to Step 3.

      • NO SIGNIFICANT DECREASE: The engine speed does not decrease significantly. Therefore, check the transmission first. Proceed to Step 4.
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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.

3. Check The Brake Pressure.

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

   Expected Results

   • The pressure is correct.

   Results

   • OK: The brake pressure is correct but the original problem is not resolved. Therefore, the transmission is the probable cause of the problem. Proceed to Step 6.

   • NOT OK: Proceed to Step 5.

4. Check For Transmission Drag.

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

   Expected Results

   • The clutch pressures are correct.

   Results

   • OK: Proceed to Step 7.

   • NOT OK: Proceed to Step 8.

5. Follow The Procedure In This Reference.

   Refer to “The Machine Does Not Move or the Machine Moves Slowly” in this module under Troubleshooting, "Machine Movement".

   Results

   • REPAIRED OK: Stop.

   • NOT OK: Proceed to Step 9.

6. 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 OK: Stop.

   • NOT OK: Proceed to Step 9.

7. Eliminate Other Possible Causes.

   The condition can be caused by several other components. Eliminate the following components as possible causes of the problem.

   1. Torque divider (converter)

   2. Transfer or bevel gears

   3. Final drives

   4. Drive shaft

   5. Axle shafts

      Expected Results

      • The original problem is resolved.

      Results

      • OK: Stop.

      • NOT OK: The cause of the problem is unknown. Use the information from the original problem to troubleshoot.

8. Follow The Procedure In This Reference.

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

   Results

   • REPAIRED OK: Stop.

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

9. Inspect The Transmission.

   1. Disassemble the transmission. Inspect the transmission for damage.

      Reference: Refer to Disassembly and Assembly, M0073303, "Transmission".

   2. Replace components or repair components that are not functioning correctly, if necessary.

   3. 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.

Harsh Shifting

Follow this procedure if harsh shifts occur. Harsh shifting can occur when the transmission shifts into certain gears or when the transmission shifts from certain gears.

Note: Before conducting any tests on the power train system, make sure that the transmission oil is up to operating temperature.

Illustration 2	g06368835

Illustration 3	g06368699

Illustration 4	g06368767

Illustration 5	g06368806

The Machine Makes an Abrupt Stop When You Shift into the NEUTRAL Position

The machine functions correctly when the transmission is engaged. However, the machine stops when the transmission is placed in the NEUTRAL position.

1. Check For The Symptom.

   1. Determine that the symptom is active.

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

      Results

      • ACTIVE: Proceed to Step 2.

      • NOT ACTIVE: The symptom is intermittent. Follow this procedure when the problem is active. Stop.

2. Check The Brake Pedal.

   1. Inspect the brake pedal. Determine if the pedal is returning to the original position.

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

   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 3.

3. Check The Brake Pressure.

   Refer to Specifications, Systems Operation/Testing, and Adjusting, M0064234, "Brake Pressure - Test".

   Expected Results

   • The pressure is correct.

   Results

   • OK: Proceed to Step 7.

   • NOT OK: Proceed to Step 4.

4. Check The Transmission Main Relief Pressure.

   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: Proceed to Step 8.

   • NOT OK: The cause of the problem may be the adjustment of the transmission relief valve. The transmission relief valve maintains the system pressure in the control section of the power train oil pump. Proceed to Step 5.

5. Adjust The Transmission Relief Valve.

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

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

   • The original problem is resolved.

   Results

   • OK: Stop.

   • NOT OK: Proceed to Step 6.

6. 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 transmission main relief pressure is correct but the original problem exists. Proceed to Step 8.

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

7. 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 OK: Stop.

   • NOT OK: 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 Machine Does Not Move or the Machine Moves Slowly” in this module under Troubleshooting, "Power Train System Pressure is Low".

   Results

   • REPAIRED OK: Stop.

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

The Transmission Does Not Change Speeds but the Machine Moves

Follow this procedure if the machine operates in both directions, but the machine only operates in a single speed.

1. 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 Troubleshooting"
   .

   Results

   • YES: The Clutch is repaired.

   Proceed to Step 5.

   • NO: Proceed to Step 2.

2. Identify The Operation.

   1. Determine the operation of the machine.

      Results

      • BI-DIRECTIONAL: Proceed to Step 3.

      • MANUAL SHIFT: Proceed to Step 4.
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   Illustration 6	g06124690

3. Test The Bi-Directional Operation.
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   Table 4

   Bi-Directional Dial
   Position	Setting
   A	Bi-Directional selector dial
   B	Throttle dial
   1	Default
   2	1.0F-2.5R
   3	2.0F-2.5R
   4	2.0F-1.5R
   5	Configurable

   1. Turn the start switch key to the ON position. Do not start the engine.

   2. Fully disengage the parking brake.

   3. The dial for the Bi-Directional function is on the left "B Post". For the D6T, available modes are "DEFAULT", "1.0F-2.5R", "2.0F-2.5R", "2.0F-1.5R", and "Configurable".

   4. Position #1 is the DEFAULT.

   5. Turn the Dial to #2 for the Bi-Directional function "1.0F-2.5R".

   6. Move the transmission control from the FORWARD position to the REVERSE position. Then, move the transmission control back to the FORWARD position. The speed display progresses through the following sequence: "1.0F", "N", "2.5R", "N", and "1.0F".

   7. Turn the Dial to #3 for the Bi-Directional function "2.0F-2.5R".

   8. Move the transmission control from the FORWARD position to the REVERSE position. Then, move the transmission control back to the FORWARD position. The speed display progresses through the following sequence: "2.0F", "N", "2.5R", "N", and "2.0F".

   9. Turn the Dial to #4 for the Bi-Directional function "2.0F-1.5R".

   10. Move the transmission control from the FORWARD position to the REVERSE position. Then, move the transmission control back to the FORWARD position. The speed display progresses through the following sequence: "2.0F", "N", "1.5R", "N", and "2.0F".

   11. Turn the Dial to #1 for the Bi-Directional function until the feature is DEFAULT/OFF.

       Expected Results

       • The Bi-Directional function operates properly.

       Results:

       • OK: Proceed to Step 4.

       • NOT OK: The Bi-Directional function does not operate properly.

       Repair: Check these components: the wiring, the electrical connectors, the circuit boards, and the electronic control module (ECM).

       Proceed to Step 5.

4. Check The Operation Of The Speed Selector.

   1. Check the operation of the Thumbroller by actuating the control in both directions to verify that proper speed changes occur.

      Expected Results

      • The Thumbroller functions properly.

      Results:

      • OK: Proceed to Step 3.

      • NOT OK: The Thumbroller does not operate properly.

      Repair: Repair or replace the components.

      Proceed to Step 5.

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

   Expected Results

   • The original problem is resolved.

   Results

   • OK: The original problem is resolved. Return the machine to service.

   • NOT OK: The cause of the problem is uncertain. Inform your dealer Technical Communicator (TC) with the information that has been gathered for possible consultation with Caterpillar. This consultation will provide instructions on the action that must be taken to resolve this problem.

The Transmission Operates in FORWARD Speeds Only

Follow this procedure if the machine shifts freely between all forward gears. However, the machine does not move when the transmission is shifted into any reverse gears.

1. Use The Message Display In Order To Check The FNR Signal From The Direction Control.

   1. Press the menu button.

   2. Arrow down to "Machine Status".

   3. Select "Powertrain" from the menu displayed.

   4. Look for the following parameters:

      • "DirSelPosSnsr#1"

      • "DirSelPosSnsr#2"

   5. These parameters should correspond to the values in Table 5.

      Expected Results

      Show/hide table

      Table 5

      FORWARD	85 ± 5%
      NEUTRAL	50 ± 10%
      REVERSE	13 ± 7%

      Results

      • OK: The direction control is within tolerance. Proceed to Step 2.

      • NOT OK: Contact the technical communicator for your Dealer for possible consultation with Caterpillar.
   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.

   Note: Ensure that these tests are conducted with the transmission shifted into the REVERSE position.

2. Check The Pressure For The No. 2 Transmission Clutch.

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

   Expected Results

   • The pressure is less than 138 kPa (20 psi).

   Results

   • OK: The pressure to the No. 2 clutch is not preventing disengagement of the clutch. Proceed to Step 3.

   • NOT OK: The No. 2 clutch is not disengaging correctly. The engagement of the No. 2 clutch may be preventing the reverse movement of the machine when REVERSE is selected. Proceed to Step 6.
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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.

3. Check The Pressure At The No. 1 Transmission Clutch.

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

   Expected Results

   • The pressure is equal to the main relief.

   Results

   • OK: The modulating valve is receiving the correct pressure. Proceed to Step 7.

   • NOT OK: Proceed to Step 4.

4. Interchange The Modulating Valves.

   1. Interchange the transmission modulating valve for the No. 1 clutch with the transmission modulating valve for the No. 2 clutch.

   2. Determine whether the problem follows the valve.

      Results

      • FOLLOWS: Proceed to Step 6.

      • DOES NOT FOLLOW: Proceed to Step 5.

5. Restore The Modulating Valves.

   1. Restore the modulating valves to the original locations.

   2. Note the suspect valve.

   3. Operate the machine under normal conditions.

      Expected Results

      • The original problem is resolved.

      Results

      • OK: An obstruction in the control valve may have been displaced during the procedure. Change the oil. Change the oil filter elements and clean the screens. Calibrate the transmission modulating valves.

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

      • NOT OK: Proceed to Step 7.

6. Replace The Transmission Modulating Valve.

   1. Replace the suspect transmission modulating valve.

   2. Calibrate the transmission modulating valves.

      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: Perform the following test for the No. 1 clutch only. Proceed to Step 7.

7. Follow The Procedure In This Reference.

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

   Results

   • REPAIRED OK: Calibrate the transmission modulating valves.

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

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

The Transmission Operates in REVERSE Speeds Only

Follow this procedure if the machine shifts freely between all reverse gears. However, the machine does not move when the transmission is shifted into any forward gears.

1. Use The Message Display In Order To Check The FNR Signal From The Direction Control.

   1. Press the menu button.

   2. Arrow down to "Machine Status".

   3. Select "Powertrain" from the menu displayed.

   4. Look for the following parameters:

      • "DirSelPosSnsr#1"

      • "DirSelPosSnsr#2"

   5. These parameters should correspond to the values in Table 6.

      Expected Results

      Show/hide table

      Table 6

      FORWARD	85 ± 5%
      NEUTRAL	50 ± 10%
      REVERSE	13 ± 7%

      Results

      • OK: The direction control is within tolerance. Proceed to Step 2.

      • NOT OK: Contact the technical communicator for your Dealer for possible consultation with Caterpillar.
   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.

   Note: Ensure that these tests are conducted with the transmission shifted into the FORWARD position.

2. Check The Pressure At The No. 1 Transmission Modulating Valve.

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

   Expected Results

   • The clutch pressure is correct.

   Results

   • OK: The pressure to the No. 1 clutch is not preventing disengagement of the clutch. Proceed to Step 3.

   • NOT OK: The No. 1 clutch is not disengaging correctly. The engagement of the No. 1 clutch may be preventing the forward movement of the machine when a FORWARD speed is selected. Proceed to Step 6.

3. Check The Pressure At The No. 2 Transmission Modulating Valve.

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

   Expected Results

   • The pressure is equal to the main relief.

   Results

   • OK: The pressure to the No. 2 clutch is correct. Proceed to Step 7.

   • NOT OK: The transmission modulating valve is the probable cause of the problem. Proceed to Step 4.

4. Interchange The Modulating Valves.

   1. Interchange the transmission modulating valve for the No. 2 clutch with the transmission modulating valve for the No. 1 clutch.

   2. Determine whether the problem follows the valve.

      Expected Results

      • The original problem is resolved.

      Results

      • FOLLOWS: Note the suspect valve. Proceed to Step 6.

      • DOES NOT FOLLOW: Proceed to Step 5.

5. Restore The Modulating Valves.

   1. Restore the transmission modulating valves to the original locations.

   2. Note the suspect valve.

   3. Operate the machine under normal conditions.

      Expected Results

      • The original problem is resolved.

      Results

      • OK: An obstruction in the valve may have been displaced during the procedure. Change the oil. Change the oil filter elements and clean the screens. Calibrate the transmission modulating valves.

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

      • NOT OK: Proceed to Step 7.

6. Replace The Transmission Modulating Valve.

   1. Replace the suspect transmission modulating valve.

   2. Calibrate the transmission modulating valves.

      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: Perform the following tests for the No. 2 clutch only. Proceed to Step 7.

7. Follow The Procedure In This Reference.

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

   Results

   • REPAIRED OK: Calibrate the transmission modulating valves.

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

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

The Transmission Does Not Operate in Specific Speeds

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.

Illustration 7	g06185965