The 2026 GMC Sierra 3500HD AT4 in 4WD Crew Cab Standard Box configuration is a heavy-duty diesel truck built equally for punishing job sites and genuine off-road terrain. Under the hood sits GMC's legendary 6.6L Duramax turbo-diesel V8, rated at 470 horsepower and a massive 975 lb-ft of torque, paired with an Allison 10-speed automatic transmission for smooth, confident power delivery under any load. That combination gives this truck the muscle to handle up to 20,000 lbs of conventional towing and up to 21,300 lbs when rigged for gooseneck or fifth-wheel. Maximum payload comes in at 4,127 lbs. If you tow heavy, this is the engine and transmission combination that serious haulers trust.

What separates the AT4 from other Sierra 3500HD trims is the off-road hardware. You get an off-road suspension package with twin-tube Rancho shocks, 11.1 inches of ground clearance, skid plates protecting the oil pan, front axle, and transfer case, and front and rear recovery hooks. The two-speed electronic Autotrac transfer case puts 4x4 capability at your fingertips, and Hill Descent Control keeps things composed on steep descents. An auto-locking rear differential and an integrated trailer brake controller round out the capability package. This is a truck that can get to the job site when lesser trucks give up.

Inside, the crew cab wraps comfort around the capability with a premium AT4-exclusive Jet Black interior with Kalahari accents. Perforated leather-appointed front seats are both heated and ventilated, second-row outboard seats are heated, and the heated leather-wrapped steering wheel takes the edge off cold mornings. You get 43.4 inches of rear legroom, dual-zone automatic climate control, 10-way power front seats with lumbar adjustment, and remote start. The GMC MultiPro Tailgate offers six load and access modes, and a spray-on bedliner keeps the cargo box protected. A 120-volt bed outlet and LED cargo lighting add practical utility.

Technology is equally comprehensive. The 13.4-inch GMC Infotainment System runs Google built-in with natural voice commands and navigation, while a 12.3-inch digital Driver Information Centre keeps critical data in your sightline. Wireless Apple CarPlay and Android Auto connect without cables, and a Bose Premium 7-speaker audio system handles the rest. The in-vehicle trailering app adds a pre-departure checklist, real-time trailer mileage tracking, and trailer tire pressure monitoring capability. Up to 14 available camera views, including HD Surround Vision and a Bed View camera, make hitching and maneuvering significantly less stressful. GMC Pro Safety covers forward collision alert, enhanced automatic emergency braking, lane keep assist, blind spot monitoring, and rear cross traffic alert.

Financing and lease options are available, trade-ins are welcome, and you can book a test drive today.

VSA 10374