The 555-horsepower Duramax 8.3-liter Turbo-Diesel V-8 and updates to the capable 6.6-liter V-8 gas engine have arrived. The new horsepower, torque, and features might have prospective GM customers wondering, “If back in the day we could deliver pizzas in 30 minutes or less, maybe with 555 horsepower and 1,230 lb-ft of torque, we can do the same with freight!” Of course, those pesky things called laws and regulations might get in the way of optimism for many operators.
“For 2027, we took GM’s proven HD validation playbook and turned up the capability — integrating new powertrain, braking, steering and chassis technologies for serious customers who push their trucks hard every day,” said Mark Dickens, Executive Chief Engineer for GM Full Size Trucks and SUVs. “HD customers don’t hold back — and neither did we.”
The new Duramax 8.3-liter Turbo-Diesel V-8 offers 555 horsepower and 1,230 lb-ft of torque. In case you’re curious like I was, Ford’s 2027 High-Output 6.7-liter Power Stroke V-8 is currently rated at 500 horsepower and 1,200 lb-ft of torque. GM’s enhanced 6.6-liter V-8 gas engine is rated at 412 horsepower and 472 lb-ft of torque when installed in heavy-duty pickups.
Earlier this week, General Motors put out a teaser video that took a direct shot at Ford. Mentioning, “a certain crosstown rival’s HD V-8 diesel engine may be referred to as the ‘Scorpion.’ But nature — or GM, in this case — always engineers a better predator: the Mongoose. Built to dominate, this diesel engine packs power, capability, and confidence.” For those unaware, Scorpion is Ford’s nickname for its 6.7-liter Power Stroke V-8.
“This new diesel engine is the culmination of decades of GM diesel development and integration,” said Norman Peralta, Executive Chief Engineer, Global Engine and Battery Systems. “From the clean-sheet architecture and combustion system to the cooling, aftertreatment and transmission calibration, this is a powertrain built with heavy-duty purpose and pride.”
In addition to the impressive performance specifications, the new Duramax is “engineered as a holistically integrated system to deliver more power, control and confidence for customers who demand maximum capability from their trucks every day.” The engine will be paired with the Allison 10-speed 10L1000 transmission equipped with “advanced shift logic.”
GM’s latest diesel engine includes the following benefits:
- A new HD diesel architecture featuring a compacted graphite iron cylinder block and fully forged crankshaft, connecting rods, and steel pistons which form a strong and durable foundation.
- Towing-focused advanced cooling and turbocharging systems that include a compact dual-stage air-to-water charge cooling system, high-efficiency variable-geometry turbocharger, and upgraded engine-cooling strategy to help the heavy-duty truck perform well under pressure.
- Improved refinement and drivability thanks to the new engine architecture, integrated intake design, advanced combustion system, and crankshaft isolation hardware for reduced noise and vibration.
- Upgraded exhaust braking capability and a new aftertreatment layout to “support heavy-duty performance, regeneration functionality and customer confidence over long-distance towing.”
The Duramax will be built at GM’s DMAX facility in Brookville, Ohio, which recently received a $920 million investment from General Motors to support high-volume production of diesel engines. The 6.6-liter V-8 gas engine will be built at GM’s Tonawanda Engine Plant in New York.
The new drivetrain is capable of towing up to 38,000 pounds and has a gross combined weight rating of up to 46,500 pounds. All that capacity is well handled thanks to updated trailering technology and upgraded undercarriage components which include a new state-of-the-art heavy-duty braking system and proprietary rack-and-pinion electric power steering system.
The “segment-first” electronic brake-boost system includes 14.6-inch front rotors, four-piston fixed front calipers, and upgraded rear hardware for improved thermal capacity. GM also designed the system to have a new pedal position that promotes less pedal travel for a more predictable feel. In previous models, the braking and power steering systems would share one hydraulic source; for the 2027s, this was eliminated to reduce complexity, remove weight, and improve on- and off-road steering at lower speeds.
So if the power steering isn’t run off hydraulics, how does it work? I’m glad you asked, Mr. or Mrs. Ghost. The previous hydraulically assisted steering system has been replaced with a rack-and-pinion electric power steering system “designed specifically for heavy-duty truck demands.” GM went in and eliminated hydraulic pumps, hoses, fluid, and related hardware to reduce traditional steering noise, lower complexity, and, of course, “improve the ownership experience.” The hardware is corrosion- and impact-resistant for job sites that may include rough terrain, road debris, and “severe-duty use.”
These new engines will be available in 2027 Chevrolet Silverado HD and GMC Sierra HD pickups, which are expected to arrive at U.S. dealerships in late 2026. Pricing has not yet been announced.
