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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 ...

Footnotes — Maintenance Schedule Additional Required Services — Severe
a) Extreme service. For vehicles mainly driven off-road in four-wheel drive or used in farming, mining, forestry, Department of Natural Resources (DNR), or snow plowing. b) Check all fuel and vapor l ...

Reporting Safety Defects to General Motors
In addition to notifying NHTSA (or Transport Canada) in a situation like this, please notify General Motors. Call 1-800-GMC-8782 (1-800-462-8782), or write: GMC Customer Assistance Center P.O. Box ...