GM's New Mongoose 8.3-Liter Duramax Diesel Makes 555 HP, 1,230 LB-FT

General Motors unveiled its next-generation Duramax: a new 8.3-liter turbodiesel V8 dubbed “The Mongoose,” rated at 555 horsepower and 1,230 lb-ft of torque. GM says the engine will be available for the 2027 Chevrolet Silverado HD and GMC Sierra HD. In proper gooseneck configuration, GM lists a maximum towing capacity of 38,000 pounds. The figures also mark a leap over the outgoing 6.6-liter Duramax, which is rated at 470 hp and 975 lb-ft, and GM positions the Mongoose as stronger than Ford’s internal-codenamed “Scorpion” Power Stroke, which is rated at 500 hp and 1,200 lb-ft. GM says both trucks should reach dealers later in 2026.