2021 GMC Sierra 2500HD — Black exterior, one-owner, 138,545 miles. Built for heavy work and confident towing, this Sierra pairs the proven DURAMAX 6.6L Turbo-Diesel V8 (B20 compatible) with an Allison 10-speed automatic transmission and two-speed Autotrac transfer case for rugged 4WD capability. Key highlights - Powerful diesel drivetrain: 6.6L Duramax V8 with Allison 10-speed automatic, exhaust brake, engine block heater, high-idle switch and 220-amp alternator for demanding applications. - Towing & trailering: Integrated trailer brake controller, heavy-duty towing/camper package, power-adjustable vertical trailer mirrors (heated and auto-dimming upper glass) and front/rear ultrasonic park assist to make hitching and maneuvering easier. - Off-road & protection: X31 Off-Road Package with skid plates and hill descent control plus spray-on GMC bed liner and bed-mounted 120V power outlet. - Safety & driver aids: Automatic Emergency Braking, Forward Collision Alert, Front and Rear Park Assist, Rear Cross Traffic Alert, Lane Change Alert with Side Blind Zone Alert. - Convenience & tech: GMC Infotainment 7" touchscreen, SiriusXM, 4G LTE Wi-Fi capable, 4.2" driver information display, remote keyless entry, steering-wheel audio controls and 120V outlet in the instrument panel. - Comfort: Power 10-way driver seat, rear window defogger, deep-tinted glass, auto-dimming rearview mirror. - Practical extras: Winter grille cover, license plate kit (front), LED cargo area lighting, tailgate with EZ-lift function. This Sierra is a capable, well-equipped heavy-duty truck for contractors, fleet buyers, or anyone who needs diesel torque, off-road readiness and modern safety technology in a work-ready package. Clean one-owner history and robust factory equipment make it a smart choice for serious towing and hauling.