Allison 1000 6-Speed Automatic, 4WD, Cocoa/Dune Leather. 4D Crew Cab Summit White 4WD Allison 1000 6-Speed Automatic Duramax 6.6L V8 Turbodiesel 60 DAY SATISFACTION GUARANTEE How does it work? The preowned vehicle must have less than 80,000 miles at the time of sale. Up... via EveryCarListed.com