Defining the all-new 2015 Chevrolet Silverado and GMC Sierra heavy-duty pickups comes down to four words: Strong, smart, capable and comfortable. The 2015 Silverado HDs are the heavy lifters in Chevrolet’s three-truck strategy, which includes the all-new 2014 Silverado 1500 and, later this year, the 2015 Colorado midsize truck. The Sierra 2500HD and 3500HD models – including Sierra Denali HD – feature bold, new styling and all-new, better-connected interiors. A Duramax 6.6L turbo-diesel engine with Allison 1000 six-speed transmission powertrain combination complements powertrain offerings. Source: GM