An 8.3-liter turbo-diesel V8 is headed for General Motors’ heavy-duty pickups, and GM rates it at 555 horsepower and 1,230 lb-ft of torque. The all-new Duramax will be offered in the 2027 Chevrolet Silverado HD and GMC Sierra HD, which GM expects to reach U.S. dealers beginning late 2026.
GM describes the engine as a clean-sheet design developed in-house. It will be built at the company’s expanded DMAX plant in Brookville, Ohio, and it is listed as an available engine rather than standard equipment.
The figures come from GM’s Sept. 24, 2026 announcement of the 2027 heavy-duty lineup, which describes the engine as delivering “best-in-class diesel horsepower and torque at 555 hp / 1,230 lb.-ft.” The class ranking is GM’s claim; the ratings are the company’s published numbers, not independent dyno results.
How the 8.3L compares with the 6.6L Duramax
The yardstick is the engine it outguns. GM’s own spec sheet for the 6.6L L5P Duramax lists 6,604 cc of displacement, 470 horsepower at 2,800 rpm and 975 lb-ft at 1,600 rpm. Against those numbers, the 8.3L adds 85 horsepower and 255 lb-ft.
The 6.6L remains the diesel on the current trucks. Chevrolet’s 2026 Silverado HD page lists the Duramax 6.6L at 470 horsepower and 975 lb-ft, with a maximum of 36,000 pounds of towing for the 3500 HD. GM’s release does not say whether the 6.6L diesel carries over alongside the new engine for 2027.
The hardware behind the numbers follows heavy-duty practice. GM describes a “compacted graphite iron cylinder block and fully forged crankshaft,” paired with the Allison 10-speed 10L1000 automatic.
Norman Peralta, GM’s executive chief engineer for global engine and battery systems, framed it as a long-running program in the release: “This new diesel engine is the culmination of decades of GM diesel development and integration. 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.”
Towing ratings for the 2027 Silverado HD and Sierra HD
GM rates the 2027 trucks for up to 20,000 pounds of conventional trailering and up to 38,000 pounds with a gooseneck hitch on properly equipped models, with a gross combined weight rating of up to 46,500 pounds. The release adds that every diesel dually model can tow “up to an available 30,000 lbs. or more.”
That 38,000-pound gooseneck figure sits 2,000 pounds above the maximum GM advertises for the current trucks. GMC’s diesel page for the 2026 Sierra Heavy Duty lists “available max towing of 36,000 lbs.” with the 6.6L diesel, matching the Chevrolet figure.
The engine is only part of the 2027 update. GM lists what it calls a segment-first rack-and-pinion electric power steering system, a segment-first electronic brake-boost system with four-piston front calipers on 14.6-inch rotors, a new Terrain Mode with one-pedal off-road control, and up to 14 available camera views for towing. On the gas side, the enhanced 6.6L V8, built at GM’s Tonawanda Engine Plant in New York, is rated at 412 horsepower and 472 lb-ft, which GM calls best-in-class standard torque among 2027 model-year HD gas engines. It shares the Allison 10L1000 transmission with the diesel.
Mark Dickens, GM’s executive chief engineer for full-size trucks and SUVs, said the company “took GM’s proven HD validation playbook and turned up the capability” for 2027. That is the company’s description of its own validation work; the trucks have not yet reached dealers.
Built in Brookville
The 8.3L will come out of GM’s DMAX facility in Brookville. GM said in the same release that it had previously invested $920 million to expand the facility for this high-volume engine program.
The next step on the record is the showroom. GM’s stated timing is that the 2027 Chevrolet Silverado HD and GMC Sierra HD are expected to arrive at U.S. dealers beginning late 2026.
Featured image: A 2024 Chevrolet Silverado 2500HD pickup. Image Credit: Deathpallie325 — CC BY-SA 4.0 / Wikimedia Commons
This article was produced with the assistance of AI and reviewed by Combat Rated editors prior to publication.