GM’s New 8.3L Duramax Delivers 555 HP, 1,230 lb-ft Of Torque, And 38,000 Pounds Max Towing

The heavy-duty pickup horsepower war has officially moved into a new phase. Just days after teasing its all-new 8.3-liter Duramax Turbo-Diesel V8, General Motors has put numbers behind the engine — and they are substantial.

The new “Mongoose” Duramax headed for the 2027 Chevrolet Silverado HD and GMC Sierra HD produces 555 horsepower and 1,230 lb-ft of torque. That represents a significant jump over the outgoing 6.6-liter Duramax, which was rated at 470 horsepower and 975 lb-ft.

Just as important, GM has now detailed how that extra output translates into towing capability.

Up To 38,000 Pounds Of Trailer

Properly configured 2027 Silverado HD and Sierra HD models will offer a maximum trailering rating of 38,000 pounds, while gross combined weight rating climbs as high as 46,500 pounds. GMC also confirms that the Sierra 3500 HD reaches the full 38,000-pound figure, with the 2500 HD topping out at 23,100 pounds.

GM says every diesel-powered dually configuration will be capable of towing at least 30,000 pounds, reinforcing that the new Duramax was designed around serious work rather than simply winning the spec-sheet horsepower battle.

The company has also reworked the hardware surrounding the powertrain. Chassis, suspension, steering, and braking systems have been recalibrated to improve stability and predictability when towing near the trucks’ maximum ratings.

More Than Just A Bigger Duramax

The new 8.3-liter Duramax remains paired with an Allison 10-speed automatic transmission, but GM has revised its shift strategies for heavy towing, including launching loaded trailers, climbing grades, and managing speed on descents. The trucks also gain updated exhaust-braking capability, along with new steering and braking hardware designed to make heavy loads easier to control.

Available trailering technology continues to play a major role as well. Silverado HD and Sierra HD buyers can get up to 14 camera views, including Transparent Trailer View, Bed View, and Surround Vision, along with trailer blind-zone monitoring and tire-pressure and temperature monitoring.

GM Comes Out Swinging

At 555 horsepower and 1,230 lb-ft, the Mongoose Duramax is a major departure from the engine it replaces. GM has paired that output with substantially revised towing hardware and a 38,000-pound maximum trailer rating, creating what is easily the most capable Duramax-powered HD pickup the company has offered to date.

Mongoose By The Numbers

The new 8.3-liter Duramax represents a major jump over the outgoing 6.6-liter L5P, but it is also entering an increasingly competitive heavy-duty diesel field.

2026 6.6L Duramax L5P: 470 hp | 975 lb-ft | 36,000-lb max towing

2027 8.3L Duramax Mongoose: 555 hp | 1,230 lb-ft | 38,000-lb max towing

2027 6.7L Cummins H.O.: 430 hp | 1,075 lb-ft | Ram 2500/3500 Heavy Duty

2026 6.7L H.O. Power Stroke: 500 hp | 1,200 lb-ft | 40,000-lb max towing

Compared with the outgoing Duramax, the new Mongoose gains 85 horsepower and 255 lb-ft of torque, while maximum available trailering increases by 2,000 pounds.

The 2027 Ram Heavy Duty’s 6.7-liter High Output Cummins remains rated at 430 horsepower and 1,075 lb-ft, giving the new Duramax a 125-horsepower and 155-lb-ft advantage on paper. Ram pairs its Cummins exclusively with the TorqueFlite HD eight-speed automatic.

Ford’s current High Output 6.7-liter Power Stroke sits much closer to the new GM engine at 500 horsepower and 1,200 lb-ft. That leaves the new Duramax with 55 more horsepower and 30 more lb-ft of torque, while Ford continues to list up to 40,000 pounds of maximum gooseneck towing in properly configured F-450 Super Duty models.