We build vehicles with Allison® five and six-speed automatic transmissions. This part of the manual covers the basics of these. With these transmissions, you will find another Allison® manual in your vehicle that goes into more detail. On the headliner, in front of and above the driver, or in some other place near the driver, you will see a label that describes important operating facts about the automatic transmission in your vehicle. Make sure you follow the instructions on this label.
Be sure to keep your parking brake set until you are ready to shift into DRIVE (D), and press the brake pedal while shifting from NEUTRAL (N) or PARK (P) to a drive gear.
All vehicles equipped with automatic transmissions can be started in PARK (P), if equipped, or in NEUTRAL (N). See the Allison® Transmission Operator's Manual in your vehicle for more information about this.
Caution: It can be dangerous to get out of the vehicle without the parking brake firmly set. The vehicle can roll. If you have left the engine running, the vehicle can move suddenly. You or others could be injured. To be sure the vehicle will not move, even when you are on fairly level ground, always set the parking brake.
Caution: Shifting into a drive gear while the engine is running at high speed is dangerous. Unless your foot is firmly on the brake pedal, the vehicle could move very rapidly. You could lose control and hit people or objects. Do not shift into a drive gear while the engine is running at high speed.
Overdrive Defeat
If your vehicle has this feature, you can select not to shift up to fifth gear. This is useful when towing or under a heavy load.
The overdrive defeat switch is located in the instrument panel to the right of the steering column.
Press the switch to limit the transmission to fourth gear. This will allow for fewer downshifts while pulling a trailer or under a heavy load. The indicator light in the switch will come on whenever overdrive defeat is active.
