This pristine, one-owner, accident-free 2025 GMC Sierra 2500HD AT4 in bold Onyx Black is a premium heavy-duty pickup engineered for serious capability, luxury, and off-road prowess. Powered by the legendary Duramax 6.6L V8 Turbodiesel delivering massive torque and towing power, it pairs with a smooth 10-speed automatic transmission and robust 4WD system featuring a 2-speed active transfer case, Hill Descent Control, and the X31 Off-Road Package for enhanced ground clearance and trail performance. A fresh oil change has been completed, and it stands out with gloss black grille accents, LED smoked amber roof marker lamps, deep-tinted glass, off-road high clearance steps (LPO), spray-on bedliner with GMC logo, and LED cargo area lightingready for work, towing, or adventure.The upscale cabin features Jet Black with Kalahari accents leather, ventilated and heated driver and front passenger seats, heated second-row outboard seats, a power sunroof, floor-mounted center console, and premium front and rear floor liners. Tech highlights include a massive multicolor 15" diagonal head-up display, Bose premium 7-speaker sound system, wireless charging, wireless phone projection, SiriusXM w/360L, steering wheel audio controls, and advanced connectivity with multiple USB ports, 120-volt outlets, and OnStar services. Safety and convenience abound with HD Surround Vision, Bed View Camera, trailer provisions, rear cross traffic alert, trailer side blind zone alert, ultrasonic park assist, and the Safety Alert Seat.Loaded with the AT4 Preferred Package, AT4 Premium Plus Package, Technology Package, Max Trailering Package, Gooseneck/5th Wheel Prep Package, and more, this top-trim Sierra 2500HD AT4 combines GMC's renowned durability, heavy-duty towing/hauling strength, and refined luxury in an off-road-capable package. It's the ultimate choice for those seeking a powerful, feature-packed diesel truck that's low-maintenance, trail-ready, and built for demanding lifestyles or long-haul confidence.