2026 GMC Sierra 2500 HD Crew Cab AT4X Pickup 4D 6 Ft Ultimate Heavy-Duty Luxury & CapabilityThis 2026 GMC Sierra 2500 HD AT4X is the perfect combination of luxury, off-road capability, and serious heavy-duty performance. Finished in an aggressive, commanding stance, the AT4X trim represents the top-tier off-road package in the Sierra HD lineup built for those who demand premium comfort without sacrificing power or rugged capability.Powered by a 6.6L V8 paired to a 10-speed automatic transmission, this Sierra HD delivers the muscle you expect whether you're towing, hauling, working, or heading off the beaten path. The Crew Cab configuration with the 6-foot bed offers the ideal balance of passenger space, practicality, and everyday usability. GMC offers the AT4X with premium off-road hardware including a factory lift, Multimatic DSSV dampers, locking differential, skid plates, and aggressive 35-inch off-road tires, making it one of the most capable heavy-duty trucks on the road.Inside, the cabi