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Personal injury or death can result from sudden machine movement. Sudden movement of the machine or release of air pressure or oil pressure can cause injury to persons on or near the machine. To help prevent possible injury before testing and adjusting any air system or hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section. |
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This check determines if the following conditions exist:
- The transmission solenoids are leaking.
- The transmission clutches engage properly.
- The torque converter lockup clutch is stuck.
Procedure
- Disconnect all the electrical harness connectors from the upshift solenoid, the downshift solenoid, and the lockup solenoid. Start the engine and run the engine at low idle.
- Engage the parking brakes and the service brakes.
- Perform the shift sequence that follows for reverse and for each forward speed.
Note: Regularly check the torque converter oil temperature. Do not allow the torque converter oil temperature to increase too much during this shift sequence. The torque converter and the transmission can be damaged by high oil temperature. Watch for any temperature warnings. If the oil temperature becomes too hot, put the transmission in NEUTRAL. The engine should then be run at approximately 1500 rpm until the temperature returns to the normal operating range.
Shift Sequence
- Manually rotate the transmission rotary selector spool to the desired speed. After the manual shift is performed, move away from the machine.
Note: Refer to Testing and Adjusting, "Transmission Hydraulic Control Clutch Pressure - Test" for the procedure on performing manual shifts.
- Gradually increase the engine rpm until the level of the rpm is approximately 1300 rpm or until the machine begins to creep forward.
- If the level of the rpm is 1300 rpm and the machine does not begin to creep forward, look at the rear end of the drive shaft. When the transmission clutch is operating correctly, a small amount of rotation will be observed in each position except NEUTRAL. The amount of rotation will be less than one complete turn.
Show/hide table
Table 1 Transmission Speed Engaged Clutches in the Transmission Neutral 1 Reverse 3 and 7 First speed 2 and 6 Second speed 1 and 6 Third speed 3 and 6 Fourth speed 1 and 5 Fifth speed 3 and 5 Sixth speed 1 and 4 Seventh speed (1) 3 and 4 Show/hide table( 1 ) This speed is not used on the 771D Quarry Trucks.
- Decrease the engine rpm to low idle. Shift to the next speed position. Repeat steps 1, 2, and 3 of the shift sequence. This will help in the identification of a slipping clutch. Continue this sequence for the remainder of the speeds until the final speed is performed.
Problem: The machine begins to creep forward before the engine rpm achieves 1300 rpm.
Probable Cause
The probable cause is the brake system. Refer to the Air System and Brakes Systems Operation/Testing and Adjusting.
Problem: The drive shaft does not turn in NEUTRAL.
Probable Cause
- The torque converter is damaged. Look for metal chips in the transmission magnetic screen. Refer to Testing and Adjusting, "Power Train Hydraulic System Troubleshooting". Perform checks.
- There is an improperly engaged transmission clutch. Refer to Testing and Adjusting, "Transmission Hydraulic Control Clutch Pressure - Test". This can cause damage to the transmission.
Problem: When a shift is made to REVERSE or to any forward speed, the engine stops running.
Note: Be sure that the lockup clutch solenoid is disconnected.
Probable Cause
The lockup clutch is stuck in the engaged position. Look for metal chips in the transmission magnetic screen. Refer to Testing and Adjusting, "Power Train Hydraulic System Troubleshooting". Perform checks.
Problem: The drive shaft turns in more speeds than NEUTRAL, but the wheels do not turn. (A clutch or the clutches do not engage in the transmission.)
Probable Cause
There is a slipping clutch. Look for debris from the clutches. Refer to Testing and Adjusting, "Power Train Hydraulic System Troubleshooting". Perform checks.
Problem: The transmission will not stay in the selected speed position. Manual shifts are difficult in any direction (upshift or downshift).
Probable Cause
The probable cause is solenoid leakage. A shift to a higher speed from the selected speed is an indication of a bad upshift solenoid. A shift to a lower speed from the selected speed is an indication of a bad downshift solenoid.