The new Sierra HD underpins the All Terrain HD concept, with a modified, production-based 4WD chassis and the Duramax diesel/Allison 1000 six-speed powertrain. The enhanced suspension and unique body dimensions, including increased ground clearance and wider track, as well as greater approach/departure angles, deliver off-road capability while maintaining HD levels of payload and trailering capacity. The All Terrain HD is painted Iridium Metallic – a dark charcoal color that reveals a reddish, anodized inflection when viewed from certain angles.
Based on the chassis of the 2011 Sierra HD trucks, the All Terrain HD features a fully boxed steel frame with exceptional strength and torsional stiffness. It incorporates the production models’ new independent front suspension and asymmetrical rear leaf-spring suspensions, but with a wider 73-inch (1,853 mm) track (front and rear) that enhances stability during off-road and highway driving. A production Sierra 2500HD has front and rear tracks of 68.8 inches (1,748 mm) and 67.3 inches (1,709 mm), respectively.
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 Sierra HD trucks. The Duramax is rated at 397 horsepower (296 kW) and 765 lb.-ft. of torque (1,037 Nm).
The powerful 6.6L Duramax is more fuel-efficient – with up to 11-percent greater fuel economy than previous versions – and reduces NOx emissions by up to 63 percent. The powertrain’s efficiency is assisted by the Allison 1000 transmission, which requires less engine power to funnel torque to the axles. It also incorporates a “smart” exhaust brake feature that helps save wear on the brakes on downhill grades, a feature available on production Sierra HDs.