Lesson #7

How to drive a vehicle with an automatic transmission.

Both the HMMWV and the M35A3 2 1/2 ton truck have automatic transmissions. Older versions of the 2 1/2 ton truck have manual transmissions.

Gearshift pattern. Gearshift patterns differ somewhat on the various models of vehicles equipped with automatic transmissions. The typical pattern is:

• "P" (park). The transmission is locked; the truck will not move. Some vehicles do not have a "P" selection. In these vehicles, "N" (neutral) takes the place of "P."

• "R" (reverse). This puts the truck in reverse for normal backing operations.

• "N" (neutral). The transmission mechanism is disengaged. The truck wheels can move by coasting, but the truck is not in gear. This selection is used for parking, if the transmission does not have a "P" (park) selection.

• "D" (drive). This is used for normal driving with light to moderate loads. The vehicle automatically downshifts and upshifts based on vehicle speed. A forced downshift occurs at slower speeds by depressing the accelerator pedal all the way to the floor.

• "2" (second). This is used for hill climbing or engine braking to slow the truck when going down a steep hill. The gearshift lever may be shifted from "D" to "2" and from "2" to "D" under most driving conditions.

• "1" (first). This is used for maximum engine braking when driving down very steep hills or when maximum performance is required to climb a very steep hill or drive through deep snow or mud.

There are some tips you should know for driving vehicles with automatic transmissions.

• Do not coast downhill in "N" (neutral).

• Do not shift the transmission gearshift lever to "P" (park) or "N" (neutral) while the truck is in motion.

• Do not race or accelerate the engine when shifting from "P" (park) or "N" (neutral) into another gear range.

• Do not shift the transmission between forward gear ranges and "R" (reverse) while operating the engine at high speed or heavy throttle.

• Do not force the transmission gearshift lever.

• Do not shift the transmission gearshift lever to "P" (park) on a hill before setting the parking brake. This puts force on the transmission and makes it difficult to shift the transmission gearshift lever out of "P" (park).

• When preparing to drive, do not release the parking brake until the transmission gearshift lever is shifted out of "P" (park).

To put the vehicle in motion:

• Start the vehicle and allow the engine to warm up according to the operator's manual.

• Shift the transmission gearshift lever to "D" (drive) for normal driving conditions.

• Apply pressure to the service brake and release the parking brake.

• Release the service brake and accelerate as needed for road, weather, and traffic conditions.

Stopping the vehicle.

• Release the accelerator pedal.

• Depress the brake pedal.

• As the vehicle begins to reduce speed, decrease brake pedal pressure.

• Stop smoothly by releasing brake pressure gradually as the stopping rate increases.

• After stopping, apply the brake just enough to keep the vehicle stationary.