New Details: GM Unveils New Duramax 8.3L Turbo-Diesel V8 for 2027 Heavy-Duty Trucks
The all-new engine leads a package of updates to the 2027 HD lineup
Source: General Motors ↗
General Motors is replacing its long-running licensed Duramax diesel with an all-new, clean-sheet 8.3L turbodiesel V8 of its own design for the 2027 Chevrolet Silverado HD and GMC Sierra HD, both expected at U.S. dealers beginning late 2026.
The new engine is GM’s first heavy-duty diesel designed, developed and manufactured entirely in-house. It is rated at 555 horsepower and 1,230 lb.-ft. of torque, which GM claims as best-in-class for diesel horsepower and torque among HD pickups, based on latest available competitive information with SAE J1349 testing. Properly equipped models will offer up to 20,000 pounds conventional trailering and up to 38,000 pounds gooseneck. Every diesel dually configuration is rated to tow 30,000 pounds or more. Gross combined weight rating reaches 46,500 pounds on select configurations.
The engine will be built at GM’s DMAX facility in Brookville, Ohio, a 1.4-million-square-foot plant that consolidates machining and assembly under one roof. GM previously invested $920 million to expand DMAX to handle the program’s volume. “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.”
The standard 6.6L gas V8, assembled at GM’s Tonawanda Engine Plant in New York, is also updated. Output rises to 412 horsepower and 472 lb.-ft. of torque, which GM rates as best-in-class standard torque among all 2027 model-year HD gas engines. Changes include a new Turbo-Jet intake manifold, revised lubrication system, engine-mounted oil cooler and a digital oil-level display. The 6.6L also pairs with the Allison 10-speed and shares the updated shift strategies.
Both powertrains gain from chassis-level changes that will matter to fleets running these trucks under load. GM is replacing the previous hydraulic-assisted steering with a rack-and-pinion Electric Power Steering system, which the company describes as a segment first for heavy-duty pickups. The system delivers approximately 30% more steering output than the current hydraulic gear, targets reduced kickback on rough surfaces and eliminates the hydraulic pump, hoses and fluid. It operates independently of engine speed and brake-assist utilization. The brake system is also new: a segment-first electronic brake-boost architecture with 14.6-inch front rotors, four-piston fixed front calipers and upgraded rear hardware. The electronic system supports Adaptive Cruise Control and Automatic Emergency Braking integration and adds diagnostics for brake fade and leak detection.
Drive modes for 2027 coordinate powertrain, steering, braking and chassis response together. Normal covers unloaded daily use. Tow/Haul adjusts engine mapping, shifting, exhaust brake, grade braking, Electric Power Steering assist and electronic brake-boost tuning for heavy loads. Off-Road loosens ABS, traction control and stability control thresholds while tuning the steering and brakes to reduce harsh feedback on loose surfaces. A new Terrain Mode, restricted to ZR2 and AT4X configurations, enables one-pedal off-road driving in 4HI and 4LO by applying braking automatically when the driver lifts off the accelerator.
Trailering visibility includes up to 14 camera views, among them Transparent Trailer View, Bed View and Surround Vision. An in-vehicle trailering app, Trailer Side Blind Zone Alert and available trailer tire pressure and temperature monitoring are also offered. MSRP and full product specifications will be released in future updates. “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.”
