2010 Hummer H3 Owner's Manual - Page 227

Driving and Operating To rock the vehicle back and forth to get out of snow, ice, or sand without damaging the transmission, see If the Vehicle is Stuck on page 9‑26. N (Neutral): In this position, the engine does not connect with the wheels. To restart the engine when the vehicle is already moving, use N (Neutral) only. Notice: Shifting out of P (Park) or N (Neutral) with the engine running at high speed may damage the transmission. The repairs would not be covered by the vehicle warranty. Be sure the engine is not running at high speed when shifting the vehicle. D (Drive): This position is for normal driving. It provides the best fuel economy. If you need more power for passing, and you are: . 9-43 Downshifting the transmission in slippery road conditions could result in skidding, see "Skidding" under Loss of Control on page 9‑6. D (Drive) can be used when towing a trailer. You may want to shift the transmission to 3 (Third) or, if necessary, a lower gear if the transmission shifts too often under heavy loads or in hilly conditions. 3 (Third): This position is also used for normal driving. However it reduces vehicle speed more than D (Drive) without using the brakes. You might choose 3 (Third) instead of D (Drive) when driving on hilly or winding roads, or when towing a trailer, so there is less shifting between gears, or when going down a steep hill. { WARNING Shifting into a drive gear while the engine is running at high speed is dangerous. Unless your foot is firmly on the brake pedal, the vehicle could move very rapidly. You could lose control and hit people or objects. Do not shift into a drive gear while the engine is running at high speed. Going less than about 55 km/h (35 mph), push the accelerator pedal about halfway down. Going about 55 km/h (35 mph) or more, push the accelerator all the way down. .