2007 GMC Acadia Owner's Manual - Page 132

When you shift from DRIVE (D) to LOW (L), the transmission will shift to a pre-determined lower gear range. The highest gear available for this pre-determined range is displayed next to the L in the DIC. See Driver Information Center (DIC) on page 232 and DIC Operation and Displays (With DIC Buttons) on page 233 or DIC Operation and Displays (Without DIC Buttons) on page 239 for more information. The number displayed in the DIC is the highest gear that the transmission will be allowed to operate in. However, your vehicle can automatically shift to lower gears as required by various driving conditions. This means that all gears below that number are available. For example, when FOURTH (4) is shown next to the L, FIRST (1) through FOURTH (4) gears are automatically shifted by the vehicle. You cannot shift into FIFTH (5) until the plus (+) button is used or you shift back into DRIVE (D) mode. While in LOW (L), the transmission will prevent shifting to a lower gear range if the engine speed is too high for the gear range you are trying to select. You have a brief period of time to slow the vehicle speed. If vehicle speed is not reduced within the timeframe allowed, the lower gear range attempted will not be available. The highest possible gear that is allowed for that engine speed will display next to the L in the DIC. Try again to slow the vehicle speed and press the minus (−) button to the desired lower gear range. Automatic Engine Grade braking is not available when the ERS is active. It is available in DRIVE (D) for both normal and Tow/Haul mode. While using the ERS, cruise control and the tow/haul mode can be used. See Tow/Haul Mode on page 133 for more information. 132