450F Backhoe Loader Transmission (Autoshift) Caterpillar

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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before the test is done.

This section provides probable causes to known problems. Since there may be several probable causes, specific inspections or instrument tests may be recommended. These inspections and tests will help to identify the causes that are most probable.

Problem

The transmission does not operate in any speed or the transmission does not engage in all speeds.

Probable Cause

1. The neutral lockout switch is engaged.

2. The parking brake is set or the parking brake switch has failed.

3. An electrical failure in the shift control or a damaged transmission control fuse.

4. Low oil pressure that is a result of the following causes:

   1. The oil level is low.

   2. Oil pump failure.

   3. Air leaks on inlet side of the pump.

   4. The transmission leaks.

5. The transmission has a mechanical failure.

   1. Clutch discs and plates have too much wear.

   2. The seals leak.

Problem

The transmission does not shift into fifth gear forward.

1. The speed sensor is not adjusted correctly.

2. The autoshift switch is in the manual mode.

Problem

The transmission does not shift.

Probable Cause

1. Air leaks on inlet side of pump.

2. The wiring to the solenoid control valve is broken or the wiring is not connected.

3. An electrical failure in shift control or a damaged transmission control fuse.

4. Low oil pressure.

Problem

The transmission gets hot.

Probable Cause

1. A temperature gauge is damaged.

2. The oil level is high.

3. The core of the oil cooler is partially open.

4. The clutch is slipping too much.

   1. The oil pressure is low.

   2. The clutch is damaged.

5. Low oil flow as a result of pump wear or extra leakage in the hydraulic system.

6. The application for the vehicle is wrong. A large load causes too much torque converter slip.

7. Air is in the oil. Air leaks on intake side of pump.

8. The torque converter relief valve is stuck open.

9. The oil in the transmission is wrong.

Problem

Pump noise that is not normal.

Probable Cause

1. Foreign material is in the transmission hydraulic system.

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

3. There is a failed suction tube or a damaged suction tube.

Problem

The transmission has noise that is not normal.

Probable Cause

1. Parts have wear or damage.

Problem

The transmission operates in forward speeds only.

Probable Cause

1. Wiring to the reverse solenoid control valve is broken or the wiring is not connected.

2. The shift control is malfunctioning or there is a damaged solenoid.

3. Discs and plates have too much wear in reverse direction clutches.

4. The seal rings leak.

5. Reverse clutch components have damage.

6. The control valve gasket has damage.

7. The forward clutch is warped.

Problem

The transmission operates in reverse speeds or in some forward speeds only.

Probable Cause

1. Wiring to the forward low solenoid control valve or the forward high solenoid control valve is broken or the wiring is not connected.

2. The shift control is malfunctioning or there is a damaged solenoid.

3. Discs and plates have too much wear in forward direction clutches.

4. The seal rings leak.

5. Forward clutch components have damage.

6. The control valve gasket has damage.

7. The reverse clutch is warped.

Problem

The Clutch engagement is slow and the transmission makes rough shifts.

Probable Cause

1. The transmission oil pressure is low.

2. The oil leaks internally.

3. The solenoid is sticking.

4. The transmission contains oil with the wrong viscosity.

Problem

Oil pressure too low.

Probable Cause

1. The oil level is low.

2. Failure of transmission oil pump.

3. There is a suction leak.

4. The oil in the transmission is wrong.

5. The torque converter inlet relief valve is stuck open.

Problem

A single clutch pressure is too low.

Probable Cause

1. The clutch has leakage.

2. The solenoid valve spool is not shifting fully.

3. Oil is leaking past the seals of the solenoid valve to the tank.