The governor valve is stuck.

Clean or replace the governor screen and/or the governor.

Refer to applicable Allison Transmission Service Manual.

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

Check the spring adjustment.

The modulator is inoperative.

Replace the modulator. Refer to Transmission Modulator Replacement .

The trimmer valve is sticking or has a broken spring.

Replace or repair the control valve body assembly.

Refer to applicable Allison Transmission Service Manual.

The control valve is sticking.

Replace or repair the control valve body assembly.

Refer to applicable Allison Transmission Service Manual.

The modulator valve is sticking.

1. Clean the valve.
2. Check the vacuum modulator.
3. Adjust the spring.

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

Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.

The selector linkage is out of adjustment.

Adjust the shift cable. Refer to Shift Cable Adjustment .