Quadrasteer is no longer available on 2WD models, standard wheel sizes have been bumped up to 17 inches and, on extended and crew cab models, a power sunroof that includes HomeLink and a deluxe overhead console in now optional. GMC takes a step backward this year with the return of rear drum brakes, as opposed to last year's four-wheel disc setup. Big changes for the Denali this year -- Quadrasteer is no longer available, and the Denali is now a crew cab model only. A gasoline/electric hybrid model is also introduced this year. Basically a "mild" hybrid, the system provides no power boost, but does allow for automatic engine startup and shutdown at stops. This truck also comes with four 120-volt AC power outlets and is the only Silverado with rear disc brakes this year. The hybrid truck is only available in Western states and Florida.