2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 456

4. Reapply the brake pedal. Then apply the parking brake and shift into P (Park). 5. If the vehicle is four-wheel-drive, be sure the transfer case is in a drive gear and not in N (Neutral). 6. Release the brake pedal. Leaving After Parking on a Hill 1. Apply and hold the brake pedal. 2. Start the engine 3. Shift into a gear 4. Release the parking brake 5. Let up on the brake pedal. 6. Drive slowly until the trailer is clear of the chocks. 7. Stop and have someone pick up and store the chocks. { WARNING: It can be dangerous to get out of the vehicle if the shift lever is not fully in P (Park) with the parking brake firmly set. The vehicle can roll. If the engine has been left running, the vehicle can move suddenly. You or others could be injured. To be sure the vehicle will not move, even when on fairly level ground, use the steps that follow. Always put the shift lever fully in P (Park) with the parking brake firmly set. If the transfer case on a four-wheel-drive vehicle is in N (Neutral), the vehicle will be free to roll, even if the shift lever is in P (Park). Be sure the transfer case is in a drive gear - not in N (Neutral). Maintenance When Trailer Towing The vehicle needs service more often when pulling a trailer. See this manual's Maintenance Schedule or Index for more information. Things that are especially important in trailer operation are automatic transmission fluid, engine oil, axle lubricant, belts, cooling system and brake system. It is a good idea to inspect these before and during the trip. Check periodically to see that all hitch nuts and bolts are tight. 5-80