2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 179

A parking brake symbol is located next to the N (Neutral) symbol as a reminder to set the parking brake before shifting the transfer case into N (Neutral). N (Neutral): Shift to this setting only when the vehicle needs to be towed. See Recreational Vehicle Towing on page 5‑49 or Towing Your Vehicle on page 5‑48. 2 m (Two-Wheel-Drive High): This setting is used for driving in most street and highway situations. The front axle is not engaged in two-wheel drive. This setting also provides the best fuel economy. 4 m (Four-Wheel-Drive High): Use this setting when you need extra traction, such as on snowy or icy roads or in most off-road situations. This setting also engages the front axle to help drive your vehicle. This is the best setting to use when plowing snow. { WARNING: Shifting the transfer case to Neutral can cause the vehicle to roll even if the transmission is in P (Park). You or someone else could be seriously injured. Be sure to set the parking brake before placing the transfer case in Neutral. See Parking Brake on page 3‑54. You can shift from Two-Wheel-Drive High to Four-Wheel-Drive High or Four-Wheel-Drive High to Two-Wheel-Drive High while the vehicle is moving. In extremely cold weather, it may be necessary to stop or slow the vehicle to shift into Four-Wheel-Drive High. 3-41