The 2026 GMC Sierra 3500 HD is ready to take on big jobs with serious towing and hauling ability. This heavy-duty truck offers two engine choices. The 6.6-liter Duramax Turbo-Diesel V8 puts out 470 horsepower and an amazing 975 pound-feet of torque. If you want a gas engine, the 6.6-liter V8 gives you 401 horsepower and 464 pound-feet of torque. Both engines pair with a 10-speed Allison automatic transmission that shifts smoothly through each gear. Drivers near Litchfield can count on 4-wheel drive (4WD) to handle tough terrain.