2001 GMC Sierra 1500 Pickup Owner's Manual - Page 108

CAUTION: (Continued) If you have four-wheel drive, your vehicle will be free to roll -- even if your shift lever is in PARK (P) -- if your transfer case is in NEUTRAL. So, be sure the transfer case is in a drive gear, two-wheel high (2H) or four-wheel high (4H) or four-wheel low (4L) -- not in NEUTRAL. See "Shifting Into PARK (P)" in the Index. If you're pulling a trailer, see "Towing a Trailer" in the Index. REVERSE (R): Use this gear to back up. If your vehicle is equipped with the Allison Transmission, the "R" may blink on the PRNDL if the shift inhibitor is active. NOTICE: Shifting to REVERSE (R) while your vehicle is moving forward could damage your transmission. Shift to REVERSE (R) only after your vehicle is stopped. If your vehicle is equipped with the Allison Transmission, do not idle in REVERSE (R) for more than five minutes. Extended idling in REVERSE (R) may cause transmission overheating and damage. Always select PARK (P) whenever idle time exceeds five minutes. To rock your vehicle back and forth to get out of snow, ice or sand without damaging your transmission, see "Stuck: In Sand, Mud, Ice or Snow" in the Index. 2-25