2013 GMC Sierra 2500HD SLE 4WD Allison 1000 6-Speed Automatic Duramax 6.6L V8 Turbodiesel Allison 1000 6-Speed Automatic, 4WD, Cloth.Proudly serving Longmont, Boulder, Denver, Loveland, Erie, Fort Collins, Thornton, Westminster, Lakewood, Broomfield, Golden, Brighton, and Greeley. Recent Arrival!Reviews: * Impressive hauling and towing capabilities; refined and quiet ride; solid build quality; responsive steering. Source: Edmunds * If you require a vehicle that can transport over 10,000 pounds without breaking a sweat, the 2013 GMC Sierra HD deserves a spot on your short list. Furthermore, most prospective HD truck buyers who place a premium on luxury will find the Sierra HD Denali worth springing for. Source: KBB.com