For full-size trucks, high peak torque is the name of the game right now, and the Big Three in Detroit know this all too well. At the top of the spectrum, Ford has its Scorpion 6.7-liter Power Stroke diesel engine, which makes up to 500 horsepower and 1,200 lb-ft of torque, whereas the standard version has 475 ponies and 1,050 lb-ft. Ram relies on the 6.7-liter Cummins ISB inline-six turbo diesel, which makes 400 ponies and 1,075 lb-ft from the H.O. tuned version. However, General Motors’ Duramax V8 engine comes dead last against the competition, but that could be on the verge of changing with what could be a new 8.3L Duramax V8 turbo diesel.
Per the guys at TFL Truck, this affectionately nicknamed “Megamax” diesel engine coming from General Motors may launch around 2026 with class-leading power and torque numbers. The yet-to-be-confirmed engine is believed to develop 600 horsepower and 1,200 lb-ft of torque. That’s more power, though similar torque to that of the Scorpion Power Stroke. As they say, there’s no replacement for displacement.
Giving the engine an extra 1.6 liters of displacement compared to the 6.6L L5P also reduces the strain on the engine, which could theoretically extend the lifespan of the diesel V8, which is crucial for commercial and vocational fleet operators. A 10-speed transmission would handle shifting duties. GM’s ultimate version of this is the Allison-branded 10L1000, which is an entirely different creature from the Allison 1000 five-speed transmission. The 10L1000 can take up to 1,033 lb-ft of torque, so it’ll need some upgrades to take on the torque of the rumored “Megamax.”
However, while we believe TFL is reporting on something accurate, it’s likely that General Motors has evaluated several displacements for its next-generation Duramax engine that would power it’s next-generation Chevrolet Silverado HD and GMC Sierra HD trucks. And it’s possible that the 8.3L is the biggest one, while the finalized displacement is different, possibly for the sake of costs, or being too thirsty for that ever-important diesel fuel. A second possibility is that this 8.3L Duramax engine is intended purely for medium duty vehicles, signaling early intent to put more effort into the commercial truck space. Regardless, it sounds like a new Duramax is on the way, and it’s refreshing to report on future engine developments happening at GM, rather than another battery-powered boondoggle.