GM’s Monster 8.3L Duramax Just Took The Power And Torque Crown From FordGuessing HeadlightsAndre NalinFri, September 25, 2026 at 8:00 PM UTCAdd us on GoogleImage Credit: General Motors.The heavy-duty diesel horsepower war has a new leader, and GM didn't exactly take the subtle route to get there. Its answer to Ford's 6.7-liter Power Stroke is a gigantic new 8.3-liter Duramax V8 nicknamed Mongoose.GM has now revealed the all-important numbers: 555 horsepower and 1,230 lb-ft of torque. Both figures eclipse Ford's high-output 6.7-liter Power Stroke V8, better known internally as the Scorpion.Ford's high-output diesel produces 500 hp and 1,200 lb-ft, giving GM an advantage of 55 hp and 30 lb-ft. The new Duramax also comfortably outruns Ram's high-output 6.7-liter Cummins, which makes 430 hp and 1,075 lb-ft.AdvertisementAdvertisementThe Mongoose will arrive in the 2027 Chevrolet Silverado HD and GMC Sierra HD, replacing GM's familiar 6.6-liter L5P Duramax. This isn't simply a displacement increase, either, as GM says the new engine was designed in-house from a clean sheet.GM Went Big With The MongooseImage Credit: General Motors.An 8.3-liter displacement makes the new Duramax significantly larger than the 6.7-liter diesels offered by Ford and Ram. Its 555 hp arrives at 2,500 rpm, while the full 1,230 lb-ft is available at just 1,400 rpm.That's a sizable jump from the outgoing L5P Duramax's 470 hp and 975 lb-ft. The Mongoose uses a compacted graphite iron block, a forged crankshaft and connecting rods, forged steel pistons, high-flow fuel injection, and a new variable-geometry turbocharger.GM also developed a dual-stage air-to-water charge-cooling system, while integrated intake and crankshaft isolation hardware are intended to reduce noise and vibration. Power is sent through an Allison-branded 10-speed automatic transmission.Ford Still Wins One Important Numbers GameHaving the most torque doesn't automatically mean having the highest tow rating. GM says properly equipped trucks with the new Duramax will tow up to 38,000 pounds using a gooseneck, an improvement from the previous 36,000-pound maximum.AdvertisementAdvertisementFord's Super Duty can still claim the bigger number here, with a maximum available gooseneck tow rating of 40,000 pounds. GM rates conventional towing at up to 20,000 pounds.Towing capacity depends on the entire vehicle configuration rather than engine output alone. The Mongoose wins the peak power and torque contest, while Ford keeps its advantage in maximum advertised gooseneck towing.GM Changed A Lot More Than The EngineThe 2027 Silverado HD and Sierra HD also ditch their hydraulic recirculating-ball steering for rack-and-pinion electric power steering. GM says the new setup should improve precision, reduce kickback, and make low-speed maneuvering easier.Electronic brake boost arrives alongside larger 14.6-inch front rotors and four-piston fixed calipers. The new electronics also allow steering and braking behavior to be adjusted according to drive mode, while the ZR2 and AT4X models gain a low-speed Terrain Mode capable of automatically applying the brakes when the driver lifts off the accelerator.AdvertisementAdvertisementThe new trucks are expected to reach U.S. dealers in late 2026. Ford may still wear the crown when the biggest trailer enters the conversation, but when the argument turns to horsepower and torque, the Mongoose now has the Scorpion beat.If you want more stories like this, follow Guessing Headlights on Yahoo so you don't miss what's coming next.