General Motors has revealed its new 8.3-liter Duramax Mongoose turbodiesel V8, a heavy-duty truck engine producing 555 horsepower and 1,230 pound-feet of torque. The engine will be available in the 2027 Chevrolet Silverado HD and GMC Sierra HD, with both trucks expected to begin reaching dealers later in 2026.

The Mongoose gives GM a substantial output advantage over the outgoing 6.6-liter Duramax, which produces 470 hp and 975 lb-ft. It also moves the Silverado HD and Sierra HD ahead of Ford’s Power Stroke diesel, rated at 500 hp and 1,200 lb-ft.

8.3-liter Duramax power and towing

GM says the new V8 will support a conventional maximum towing rating of up to 20,000 pounds when the trucks are properly equipped. Add a suitable gooseneck setup in the bed, and maximum towing capacity rises to 38,000 pounds.

That rating applies to both the 2027 Chevrolet Silverado HD and 2027 GMC Sierra HD. The Mongoose is therefore positioned as a high-output option for buyers who need substantial trailer capacity, rather than simply a headline-grabbing engine upgrade.

Chassis upgrades for the Silverado HD and Sierra HD

The engine arrives alongside several hardware changes intended to improve the trucks’ towing behavior. Both models will use a new electronic power steering system. According to GM, it provides more precise steering feel, reduced kickback and quieter operation.

GM is also fitting larger brakes with four-piston front calipers. Improved turbocharger technology and upgraded cooling features are included as part of the package, helping support the Mongoose’s higher output and the demands of heavy-duty hauling.

Availability and expected pricing

GM has not yet announced how much the 8.3-liter Duramax will cost. The automaker says trucks equipped with the engine should begin arriving on dealer lots later in 2026, ahead of the 2027 model year.

Pricing and exact availability by trim should become clearer as the launch approaches. For now, the key takeaway is a new GM diesel that leads Ford’s Power Stroke on both horsepower and torque while offering up to 38,000 pounds of gooseneck towing capacity.