768C TRACTOR & 769C TRUCK POWER TRAIN: Troubleshooting Part 2

Problem: Transmission does not operate in Fourth and Fifth speeds.

PROBABLE CAUSE:

1. No. 5 clutch not engaged (slips) because of:

a. Low oil pressure.

b. Discs and plates have too much wear.

c. Clutch has parts that are broken.

Problem: Transmission does not operate in Sixth and Seventh speeds.

PROBABLE CAUSE:

1. No. 4 clutch not engaged (slips) because of:

a. Low oil pressure.

b. Discs and plates have too much wear.

c. Clutch has parts that are broken.

Problem: Transmission does not operate in Second, Fourth and Sixth speeds.

PROBABLE CAUSE:

1. No. 3 clutch not engaged (slips) because of:

a. Low oil pressure.

b. Discs and plates have too much wear.

c. Clutch has parts that are broken.

Problem: Transmission does not operate in Third, Fifth and Seventh speeds.

PROBABLE CAUSE:

1. No. 2 clutch not engaged (slips) because of:

a. Low oil pressure.

b. Discs and plates have too much wear.

c. Clutch has parts that are broken.

Problem: Transmission does not operate in Reverse and First speeds.

PROBABLE CAUSE:

1. Torque converter failure.

2. No. 1 clutch not engaged (slips) because of:

a. Low oil pressure.

b. Discs and plates have too wear.

c. Clutch has parts that are broken.

Problem: Transmission makes shifts rapidly (hunts).

PROBABLE CAUSE:

1. Operation of governor cut-off valve not correct.

2. Bad friction between wheels and ground.

3. Operation of shift governor not correct.

4. Shift points out of adjustment.

Problem: Transmission does not make a shift.

PROBABLE CAUSE:

1. Low oil pressure.

2. Shift points out of adjustment.

3. Operation of governor cut-off valve not correct.

4. Operation of hold valve not correct.

5. Operation of shift governor not correct.

6. Transmission controls held by detents, valve spools or linkage.

7. Wiring harness or electrical switches have a defect.

Problem: Transmission does not make a shift up or down.

PROBABLE CAUSE:

1. Low oil pressure.

2. Shift points out of adjustment.

3. Operation of shift governor not correct.

4. Operation of hold valve not correct.

5. Control linkage broken or out of adjustment.

6. Automatic selector spool cannot move.

7. Shift solenoids have a defect.

Problem: Transmission shifts up or down at wrong time.

PROBABLE CAUSE:

1. Control linkage broken or out of adjustment.

2. Shift points out of adjustment.

3. Operation of shift governor not correct.

4. Pressure reduction valves not moving and giving very low or no reference pressure.

5. Transmission electrical controls (switches) have a defect.

Problem: Transmission goes beyond a speed without stopping in that speed and will not shift down lower than a specific speed.

PROBABLE CAUSE:

1. Automatic selector spool will not move out of its bore in the valve body.

2. Reference pressure too high.

Problem: Transmission will not make a shift down beyond a specific speed but makes a shift up normally beyond that same specific speed.

PROBABLE CAUSE:

1. Automatic selector spool will not move to the inside of the valve body.

2. Operation of shift governor not correct.

Problem: Transmission operation, with hot oil, is not smooth.

PROBABLE CAUSE:

1. Bolts in valve body not tightened correctly, which causes the parts of the body not to fit or operate.

2. Torque converter not in operation during shifts.

Problem: Torque converter gets hot.

PROBABLE CAUSE:

1. Bad temperature gauge.

2. Mechanical failure of torque converter.

3. Too much oil leakage in torque converter.

4. Not enough oil to torque converter because of:

a. Oil pump failure.

b. Too much oil leakage into transmission.

c. Operation of inlet relief valve not correct.

5. Too much restriction in oil cooler or oil lines.

6. Too much operation of machine at or near stall speed.

7. Too much oil in torque converter because of:

a. Failure in scavenge pump.

b. Flow of oil through screen assembly is stopped.

Problem: Pump noise not normal.

PROBABLE CAUSE:

1. Loud sounds at short intervals, that give an indication that particles are in the pump, are caused by pump cavitation.

2. A constant loud noise is an indication of pump failure.

3. Air at the inlet side of the pump (aeration).

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768C TRACTOR & 769C TRUCK POWER TRAIN: Troubleshooting Part 2 2013-02-05T11:15:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown