Overview Two engines are offered on the 2018 GMC Sierra 3500HD, a 6.0-liter V-8 rated at 360 hp and 380 lb-ft of torque and a 6.6-liter turbodiesel V-8 with 445 hp and 910 lb-ft. Both engines are ...

RWD dually gasoline variant. For conventional towing, the Sierra 3500HD goes as high as 20,000 pounds with the diesel engine. With a fifth wheel, towing capacity maxes out at a whopping 31,800 pounds.