2021 GMC Sierra 1500 AT4 | 3.0L Duramax Diesel | Crew Cab 4x4 | Newberg Chevrolet Off-road capability, diesel efficiency, and premium AT4 equipment come together in this 2021 GMC Sierra 1500 AT4. Finished in Onyx Black over Jet Black with Kalahari accents and showing 76,825 miles, this Crew Cab 4WD pairs GMC's 3.0L Duramax turbo-diesel inline-six with a 10-speed automatic transmission. The 3.0L Duramax is factory rated at 277 horsepower and 460 lb-ft of torque for 2021, delivering strong low-rpm pulling power with the smooth character of an inline-six. Paired with the 10-speed automatic, it gives this Sierra an appealing combination of highway manners, torque, and diesel efficiency. AT4 is GMC's purpose-built premium off-road trim. Its factory hardware includes a 2-inch suspension lift, Rancho monotube shocks, skid plates, Hill Descent Control, an automatic locking rear differential, two-speed Auto Trac transfer case, all-terrain tires, and distinctive red recovery hooks. That gives the AT4 real capability beyond its aggressive appearance. The Onyx Black exterior works especially well with AT4's darker trim and rugged stance. Inside, the Jet Black cabin with Kalahari accents is one of the trim's signature details, creating an upscale environment that still looks unmistakably different from a conventional Sierra SLT. AT4 equipment includes leather-appointed seating, heated and ventilated front seats, heated rear outboard seats, a heated steering wheel, dual-zone automatic climate control, remote start, and power-adjustable front seating. Crew Cab dimensions provide generous rear passenger room and useful secure storage for work gear, family travel, or recreation. Modern GMC infotainment brings smartphone integration, touchscreen controls, driver information displays, and trailering-oriented technology into the cabin. Because no VIN-specific factory window sticker was provided, buyers should verify this truck's exact optional packages, cameras, audio system, sunroof, driver-assistance features, and trailering equipment during inspection. At 76,825 miles, this Sierra has been driven, so service history and condition should be part of the buying decision. Buyers should evaluate tires, brakes, suspension, 4WD operation, diesel emissions-system operation, fluids, and overall maintenance history. If towing is part of your plans, verify the door-jamb payload certification, axle ratio, GVWR/GCWR, hitch equipment, and specific trailer rating for this truck and your intended application. For shoppers comparing a Chevrolet Silverado 1500 LT Trail Boss, Ram 1500 Rebel, Ford F-150 Tremor, Toyota Tundra, or another premium off-road pickup, the Sierra AT4 adds something especially appealing: 460 lb-ft of Duramax torque, factory off-road hardware, Crew Cab versatility, and a premium interior. Searching for a 2021 GMC Sierra 1500 AT4 for sale, 3.0L Duramax Sierra, diesel AT4, used Crew Cab 4x4, Onyx Black GMC truck, or off-road diesel pickup near Portland? This Sierra deserves attention throughout Newberg, Mc Minnville, Yamhill County, Sherwood, Wilsonville, Beaverton, Hillsboro, Portland, and Salem.3.0L DURAMAX TURBO-DIESEL I6 • 277 HP • 460 LB-FT • 10-SPEED AUTOMATIC • 4WD • AT4 • 2-INCH FACTORY LIFT • RANCHO SHOCKS • AUTO-LOCKING REAR DIFFERENTIAL • ONYX BLACK • KALAHARI-ACCENTED INTERIOR • 76,825 MILES Available now at Newberg Chevrolet. With Duramax torque, AT4 off-road hardware, premium interior appointments, and Crew Cab practicality, this Sierra delivers a compelling mix of diesel capability and everyday refinement. VIN: 3GTU9EET9MG120159 Stock #: P4663