GM Service Manual Online
For 1990-2009 cars only

Object Number: 1722334  Size: B3

Vehicles with an automatic transmission have a tow/haul mode. The tow/haul mode adjusts the transmission shift pattern to reduce shift cycling, providing increased performance, vehicle control, and transmission cooling when towing or hauling heavy loads.

The selector button is located on the end of the shift lever. Turn the tow/haul on and off by pressing the button. When the tow/haul is on, a light on the instrument panel cluster will come on.

See Tow/Haul Mode Light for more information.

Also see Tow Haul Mode under Towing a Trailerfor more information.

Tow/Haul Mode (Allison Transmission® or Hydra-Matic® 6-Speed Automatic Transmission)


Object Number: 1836232  Size: B3

Vehicles with an Allison or Hydra-Matic® 6-speed automatic transmission® have a tow/haul mode. The tow/haul mode adjusts the transmission shift pattern to reduce shift cycling, providing increased performance, vehicle control, and transmission cooling when towing or hauling heavy loads.

Turn the tow/haul mode on and off by pressing the button, located on the end of the shift lever. When the tow/haul is on, a light on the instrument panel cluster will come on.

See Tow/Haul Mode Light for more information.

Also see "Tow Haul Mode" under Towing a Trailer for more information.

Grade Braking (Allison Transmission® or Hydra-Matic® 6-Speed Automatic Transmission)

The Grade Braking shift modes can be activated by pressing the button on the end of the shift control lever. While in Range Selection Mode , Grade Braking is deactivated allowing the driver to select a desired range of gears.

Grade Braking is only active while the Tow/Haul Mode is selected and you are not in the Range Selection Mode. See "Tow/Haul Mode listed previously and Automatic Transmission Operation for more information on the Range Selection Mode. Grade Braking assists in maintaining desired vehicle speeds when driving on downhill grades by automatically implementing a shift schedule that utilizes the engine and transmission to slow the vehicle. This reduces wear on the braking system and increases control of the vehicle. Grade Braking monitors vehicle speed, acceleration, engine torque and brake pedal usage. Using this information, it detects when the truck is on a downhill grade and the driver desires to slow the vehicle by pressing the brake.

Also see Towing a Trailer for more information.

Cruise Grade Braking (Allison Transmission® or Hydra-Matic® 6-Speed Automatic Transmission)

Cruise Grade Braking assists when driving on a downhill grade. It maintains vehicle speed by automatically implementing a shift schedule that uses the engine and the transmission to slow the vehicle. Cruise Grade Braking operates while Cruise Control is engaged in Tow/Haul mode to assist in maintaining vehicle speed under loaded vehicle conditions. It utilizes vehicle acceleration and deviation from desired speed to determine the correct gear for the operating condition. If vehicle speed is above the desired speed the transmission will downshift to slow the vehicle. If vehicle speed is near or below desired speed the trans will upshift, allowing vehicle speed to increase.

While in the Range Select Mode (RSM) mode, cruise grade braking is not available.

See Automatic Transmission Operation.