GM Service Manual Online
For 1990-2009 cars only

Object Number: 1722334  Size: B3

If your vehicle has an automatic transmission, it has a tow/haul mode. If your vehicle has an Allison or Hydra-Matic® 6-speed automatic transmission see "Tow/Haul Mode (Allison or Hydra-Matic® 6-Speed Automatic Transmission®) following. 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 Trailer for more information.

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


Object Number: 1836232  Size: B3

If your vehicle has an Allison or Hydra-Matic® 6-speed automatic transmission®, it has 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. See the diesel supplement for information on Cruise Grade Braking.

Also see Towing a Trailer for more information.