Engineered and built to get things done – the 2014 Sierra Heavy Duty doesn’t compromise. Rebuilt from the ground up to provide excellent tailoring and payload. The Sierra HD is known for getting the toughest jobs accomplished. An available Allison 1000 six-speed automatic transmission coupled with the Duramax Diesel 6.6L delivers segment leading power with 397 horsepower and 765 pound-feet of torque. GMC has extended its exclusive Denali line to the sierra heavy Duty lineup – an HD offering of Denali’s unique combination of distinctive style premium features and capability. Choose the best in technology with available XM NavTraffic – a GPS Navigation system with real-time traffic data and construction and accident updates. XM Radio USB connectivity and an available Bose premium speaker system with a sub-woofer in the center console let you personalize your driving experience. Professional Grade. Impressive build. The 2014 Sierra Heavy Duty.