D6T Track-Type Tractor Electrohydraulic System Caterpillar

Machine Movement

Usage:

D6T 2B3

Before you complete any procedure, read Troubleshooting, "Machine Preparation for Troubleshooting" in this module.

Problem List

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.

If the brake pressure is correct, then the brake system is eliminated as the probable cause of the problem. Thus, sufficient pressure is sent to the brake to release the brake. Therefore, clutch engagement in the transmission is the probable cause.

If the brake pressure is not correct, then the brake system is the probable cause of the problem. Next, a check of the system pressure determines if the system pressure is high enough. The system pressure allows the brake control valve to supply sufficient pressure to the brakes.

If the system pressure is correct, then check the proportional solenoid valves. This check guides the diagnosis of the problem to the brake control valve or to the brakes.

Troubleshooting Test Steps

Show/hide table

Table 1
Troubleshooting Test Steps	Values	Results
1. Check for the symptom A. Determine that the symptom is active. B. Complete this procedure only if the symptom is active.	The symptom is active.	OK - The symptom is active. Proceed to Test Step 2. NOT OK - If the symptom is not active, oil contamination could be the problem. Repair: Change the power train oil. Change the oil filter element and clean the screens. Proceed to Test Step 11.
2. Check The Brake Pressure A. 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. Note: Refer to Testing and Adjusting, M0064234, "Brake Pressure - Test".	The pressure is correct.	OK - The pressure is correct. Proceed to Test Step 3. NOT OK - The pressure is not correct. Proceed to Test Step 4.
3. Check For Transmission Drag A. Place pressure gauges on all transmission clutches. B. Set engine to Low Idle. C. Disengage the parking brake. D. Press down the service brake pedal to engage the brakes. E. Shift through all the transmission speeds. F. Check that the proper clutches engage for each gear. G. Check that the clutches disengage properly for each gear. The clutch that is disengaged should have a pressure below 137 kPa (20 psi).	The transmission clutches engage and the transmission clutches disengage properly.	OK - The transmission clutches engage and the transmission clutches disengage properly. Note: The engagement of the transmission clutches was eliminated as the source of the problem. Since the brake pressure was correct, then the brake control valve was eliminated as the cause of the problem. Therefore, the brake is the probable cause of the problem. Proceed to Test Step 5. NOT OK - The clutch does not engage. Proceed to Test Step 6. Repair: The clutch does not disengage. Proceed to Test Step 7.
4. Check The System Pressure A. Check the system pressure. Note: Refer to Testing and Adjusting, M0064234, "Relief Valve (Transmission) - Test and Adjust".	The system pressure is correct.	OK - The system pressure is correct. Repair: The brake pressure is not correct. Next, inspect the brake control valve. Proceed to Test Step 9. 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 Test Step 8.
5. Check The Brakes Note: The brake pressure is correct and the engagement of the transmission clutches is correct. Therefore, the brakes are the probable cause of the problem. A. Disassemble the brakes. B. Check these components of the brakes for failure: 1. Seals. 2. Splines. 3. Friction discs. 4. Brake plates. C. Replace any damaged components, if necessary. D. Calibrate the brakes. Note: Refer to Testing and Adjusting, M0064234, "Calibration" for the appropriate calibration procedure.	The original problem is resolved.	OK - The original problem is resolved. Proceed to Test Step 11. NOT OK - The cause of the problem is uncertain. Call technical support. Note: Contact the Technical Communicator with the information that has been gathered at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Proceed to Test Step 11.
6. Follow The Procedure In This Reference A. Refer to “The Transmission Clutch Does Not Engage” in this module under Troubleshooting, "Transmission Clutch".	The original problem is resolved.	OK - The original problem is resolved. Proceed to Test Step 11. NOT OK - The cause of the problem is uncertain. Call technical support. Note: Contact the Technical Communicator with the information that has been gathered at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Proceed to Test Step 11.
7. Follow The Procedure In This Reference A. Refer to “The Transmission Clutch Is Engaged And The Clutch Does Not Release” in this module under Troubleshooting, "Transmission Clutch".	The original problem is resolved.	OK - The original problem is resolved. Go to Test Step 11. NOT OK - The cause of the problem is uncertain. Call technical support. Note: Contact the Technical Communicator with the information that has been gathered at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Proceed to Test Step 11.
8. Follow The Procedure In This Reference A. Refer to “Power Train System Pressure Is Low” in this module.	The original problem is resolved.	OK - The original problem is resolved. Go to Test Step 11. NOT OK - The original problem is not resolved. Go to Test Step 10.
9. Replace The Proportional Solenoid Valves A. Replace the proportional solenoid valves. B. Check the operation of the machine for the original problem.	The original problem is resolved.	OK - The original problem is resolved. Repair: Calibrate the brakes. Note: Refer to Specifications, Systems Operation / Testing and Adjusting, M0064234, "Calibration" for the appropriate calibration procedure. Proceed to Test Step 11. NOT OK - The original problem is not resolved. Go to Test Step 10.
10. Manually Inspect The Brake Control Valve A. Disassemble the brake control valve and inspect the valve for damage. B. Repair the components and/or replace the components, if necessary. C. Calibrate the brakes. Note: Refer to Testing and Adjusting, M0064234, "Calibration" for the appropriate calibration procedure.	The original problem is resolved.	OK - The original problem is resolved. Proceed to Test Step 11. NOT OK- The cause of the problem is uncertain. Call technical support. Note: Contact the Technical Communicator with the information that has been gathered at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Proceed to Test Step 11.
11. Check If The Original Problem Remains A. Turn the key switch to the ON position. B. Operate the machine. C. Stop machine and engage the parking brake. D. Check to see if the original problem still exists.	The original problem is resolved.	OK - The original problem is resolved. Resume machine operation. STOP. NOT OK - The original problem is not resolved. Repair: Recheck the circuit and perform this procedure again. Note: Contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. STOP.