2012 GMC Sierra Owner's Manual - Page 314

9-38 Driving and Operating Notice: Spinning the tires or holding the vehicle in one place on a hill using only the accelerator pedal may damage the transmission. The repair will not be covered by the vehicle warranty. If you are stuck, do not spin the tires. When stopping on a hill, use the brakes to hold the vehicle in place. vehicle's transmission and vehicle speed while driving down hill or towing a trailer by letting you select a desired range of gears. To use this feature, do the following: 1. Move the shift lever to M (Manual Mode). 2. Press the plus/minus buttons, located on the steering column shift lever, to select the desired range of gears for current driving conditions. When M (Manual Mode) is selected a number displays next to the M, indicating the current gear. This number is the highest gear that can be used. However, the vehicle can automatically shift to lower gears as it adjusts to driving conditions. This means that all gears below that number are available. When 5 (Fifth) is selected, 1 (First) through 5 (Fifth) gears are automatically shifted by the vehicle, but 6 (Sixth) cannot be used until 1 (First): For the Hydra-Matic 4-Speed transmission this position reduces vehicle speed even more than 2 (Second) without using the brakes. You can use it on very steep hills, or in deep snow or mud. If the shift lever is put in 1 (First) while the vehicle is moving forward, the transmission does not shift into first gear until the vehicle is going slowly enough. For an Allison Transmission or Hydra-Matic 6-Speed transmission, this position reduces vehicle speed without using the brakes. You can use it for major/severe downgrades and off-road driving where the vehicle would otherwise accelerate due to steepness of grade. When you shift to 1 (First) it provides the lowest gear appropriate to current road speed and continues to downshift as the vehicle slows, eventually downshifting to 1 (First) gear. Manual Mode Range Selection Mode (Allison® Transmission or Hydra-Matic® 6-Speed Transmission) The vehicle may have a Range Selection Mode. The Range Selection Mode helps control the