1999-2006 GMC Sierra: Year-to-Year Changes

2000 GMC Sierra: A new 4-door extended-cab body replaced the 3-door setup after the 2000 model year began. Both rear doors were hinged at the back, and could not be opened or closed independently of the front doors. Sierras came in SL, SLE, and top-of-the-line SLT trim. Heavy-duty models based on the previous design remained on sale, named the Sierra Classic. Both V8 engines gained 15 horsepower this year, and peak towing capacity (when properly equipped) grew by 700 to 11,200 pounds. A factory-installed tonneau cover was newly optional for Wideside cargo beds.

2001 GMC Sierra: Traction control became an option for 2WD Sierras with an automatic transmission. Early in 2001, a new Crew Cab body style arrived, with four front-opening side doors, matching the similar body offered by Ford. GMC added a new performance-oriented C3 model to its lineup, equipped with a 6.0-liter V8 that delivered 325 horsepower. Chevrolet did not get a comparable model for its Silverado series. The C3 had unique front-end styling and exterior trim, as well as a sport suspension with 17-inch tires, bigger brakes, a heavy-duty towing package, tubular side steps, and extra amenities including a leather interior. GM's OnStar emergency/communications system was standard on the C3, and optional on SLT pickups. The C3 had a new permanently engaged 4WD system, which lacked low-range gearing.

2002 GMC Sierra: In 2002, Sierra Denali introduced GM's Quadrasteer 4-wheel steering system, which was designed to decrease the turning radius at low speed and to aid stability at higher speeds. The Quadrasteer option at midyear was extended to Silverado as well as to mainline extended-cab 2WD and 4WD Sierras; it included a special 6.5-ft box with flared fenders. Also new for Sierra was a Professional Package option that included exclusive interior storage features, such as a refrigerated console compartment and room for hanging files, plus specific exterior trim.

2003 GMC Sierra: All models got minor exterior styling changes and revamped dashboard and seats. Among new options were premium Bose audio and XM satellite radio. Rear-seat DVD entertainment is a new Crew Cab option.

2004 GMC Sierra: A new light-duty crew cab was added midyear, which has a shorter bed than the previous 1500 Heavy Duty Crew Cab. Also, base models got standard chrome exterior trim and cruise control in 2004 and SLEs got standard fog lamps.

2005 GMC Sierra: A new flagship body style, more available V8 power, and limited-edition gas-electric hybrid version highlight 2005 for Sierra. For '05, Denali is a Crew Cab instead of an extended cab. Joining the 295-hp 5.3 for '05 is a high-output version with 310 hp; it's available for short-bed 4WD extendeds. Denali uses a 6.0 with 345 hp, a 20 hp increase from 2004. Midyear, a Performance Edition package became available for short-bed 2WD LS/LT extended-cab models. The option includes the Heavy-Duty Trailering package, the Denali 6.0 V8, and 20-inch wheels and tires.

2006 GMC Sierra: No major changes for the 2006 Sierra.