2005 Pontiac Grand Prix Owner's Manual - Page 288

Driving On Grades Reduce speed and shift to a lower gear before starting down a long or steep downgrade. If the vehicle is not shifted down, the brakes may have to be used so much that they would get hot and no longer work well. On a long uphill grade, shift down and reduce the vehicle's speed to around 45 mph (70 km/h) to reduce the possibility of engine and transaxle overheating. If the vehicle has overdrive, it may be driven in THIRD (3) instead of AUTOMATIC OVERDRIVE (D). Parking on Hills {CAUTION: You really should not park your vehicle, with a trailer attached, on a hill. If something goes wrong, your rig could start to move. People can be injured, and both your vehicle and the trailer can be damaged. But if the rig ever has to be parked on a hill, here is how to do it: 1. Apply the regular brakes, but do not shift into PARK (P) yet. 2. Have someone place chocks under the trailer wheels. 3. When the wheel chocks are in place, release the regular brakes until the chocks absorb the load. 4. Reapply the regular brakes. Then apply the parking brake, and then shift to PARK (P). 5. Release the regular brakes. 4-46