The governor valve is stuck.

Clean or replace the governor screen and/or the governor. Refer to Allison service manuals.

The valve spring of the vacuum modulator is not properly adjusted, or the vacuum hose is kinked or leaking.

Check the spring adjustment. Refer to Allison service manuals.

The mechanical actuator cable is kinked, broken, or not properly adjusted.

Replace, adjust, or repair the cable. Refer to Allison service manuals.

The mechanical actuator is obstructed.

1. Check the actuator.
2. Replace the actuator if necessary.

Refer to Allison service manuals.

The modulator is inoperative.

Replace the modulator. Refer to Transmission Modulator Replacement and Transmission Modulator Cable Adjustment .

The trimmer valve is sticking, or has a broken spring.

Replace or rebuild the control valve body assembly. Refer to Allison service manuals.

The control valve is sticking.

Replace or rebuild the control valve body assembly. Refer to Allison service manuals.

The modulator valve is sticking.

1. Clean the valve.
2. Check the vacuum modulator. Refer to Vacuum Modulator Inspection .
3. Adjust the spring.

The engine idle speed in neutral to drive is too fast.

Adjust the engine idle screw. Refer to Rough, Unstable, or Incorrect Idle and Stalling in Engine Controls.

The selector linkage is out of adjustment.

Adjust the linkage. Refer to Shift Cable Adjustment or Shift Cable Adjustment .