See also:

Four-Wheel Drive
If the vehicle has Four-Wheel Drive, you can send the engine's driving power to all four wheels for extra traction. ...

Trailer Brakes
A loaded trailer that weighs more than 450 kg (1,000 lbs) needs to have its own brake system that is adequate for the weight of the trailer. Be sure to read and follow the instructions for the trailer ...

Customer Assistance Offices (U.S. and Canada)
GMC encourages customers to call the toll-free number for assistance. However, if a customer wishes to write or e-mail GMC, the letter should be addressed to: United States GMC Customer Assistance ...