GMC Previews Sierra All Terrain HD Concept Ahead of Detroit Show

General Motors will be presenting an ultra-tough concept study based on the four-door 2011 GMC Sierra HD pickup truck at the rapidly approaching Detroit Motor Show in mid-January. The GMC Sierra All Terrain HD study is highlighted by its rough n' tough exterior design and enhanced all-road capability. Shorter in overall length than production Sierra HD models, the concept boasts a unique