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Powertrain details
The GMC Sierra All Terrain HD concept is propelled by the new, production 6.6L Duramax turbo-diesel V-8 and Allison 1000 six-speed automatic transmission powertrain combination offered in the 2011 ...

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 ...

Center High-Mounted Stoplamp (CHMSL) and Cargo Lamp
To replace one of these bulbs: 1. Remove the two screws and lift off the lamp assembly. A. Cargo Lamp B. Center High-Mounted Stoplamp (CHMSL) Bulb 2. On the reverse side of the lamp assembly, r ...