The standard 360-horsepower 6.0-liter Vortec V8 engine's new camshaft profile helps the engine produce more torque lower in the rpm band, for improved launch feel and a greater feeling of overall performancewhen towing a trailer and at higher altitudes. The revised and optional 397-hp/765 lb-ft torque (335-hp/685 lb-ft torque with Box Delete option) B20 biodiesel-capable Duramax 6.6-liter diesel is more powerful and durable, and the Allison 1000 transmission is stronger for 2011. The stiffer, fully-boxed frame improves durability and ride, while supporting increased capability. The redesigned torsion bar front suspension allows for a greater front Gross Axle Weight Rating (GAWR). The rear suspension uses wider leaf springs - now asymmetrical to reduce axle hop - that contribute to improved ride and handling characteristics and increased rear GAWR. Larger brakes deliver smoother, more immediate and confident-feeling performance and diesel engines now include an exhaust brake. Stability control, hill start assist and a trailer sway control system are standard on single rear wheel trucks. Available features include mobile WiFi, USB connectivity, rear back-up camera, Bluetooth connectivity, XM satellite radio, OnStar 9.0 and a navigation system. A new frame, an improved Vortec V8, a new Duramax diesel and Allison transmission, new front and rear suspensions, and an improved brake system combine to make GMC Sierra 3500HD one of the most capable line of trucks on the road.