General Motors is putting a much larger diesel engine at the center of its 2027 Chevrolet Silverado HD and GMC Sierra HD, giving its heavy-duty pickups a major powertrain upgrade at a time when towing capability remains one of the most important reasons buyers choose full-size trucks.
GM has introduced an all-new 8.3-liter Duramax turbo-diesel V8 for the 2027 Silverado HD and Sierra HD. According to GM, the new engine produces 555 horsepower and 1,230 pound-feet of torque, figures the company describes as best in class among diesel engines in the segment.
The new Duramax is also the first clean-sheet heavy-duty diesel V8 designed, developed, and manufactured in-house by GM.
The numbers are significant because GM is not simply increasing displacement. It is replacing its existing 6.6-liter Duramax diesel with a completely new architecture designed around the demands of heavy-duty pickup customers. The move puts GM directly into the horsepower and torque battle with Ford and Ram, where diesel output has become a major selling point.
The new engine arrives as part of a broader update to the 2027 Silverado HD and Sierra HD. GM is also introducing electric power steering, an electronic brake-boost system, revised trailering technology, and updated drive modes.
The New 8.3-Liter Duramax Raises the Stakes.
The 8.3-liter Duramax is the headline change. GM says its new diesel uses a compacted graphite iron cylinder block, a fully forged crankshaft, forged connecting rods, and steel pistons to create a foundation designed for heavy-duty use.
The engine also receives a dual-stage air-to-water charge-cooling system and a variable-geometry turbocharger. GM says the cooling and turbocharging systems were developed to maintain consistent performance while towing heavy trailers, climbing grades, and working under sustained loads.
The engine is paired with an Allison 10-speed automatic transmission. GM says the transmission and engine calibration are designed to keep the powertrain in an effective operating range while improving acceleration, grade performance, and downhill control.
GM has also upgraded the exhaust braking system. For drivers pulling heavy trailers through mountain roads, controlling speed on descents without relying entirely on the service brakes can reduce brake heat and make towing more predictable.
The new Duramax will be built at GM’s expanded DMAX facility in Brookville, Ohio. GM previously invested $920 million to expand the facility for the high-volume production program. Bringing engine machining and assembly together at the 1.4-million-square-foot plant is intended to support production of the new powertrain at scale.
GM has also enhanced the 6.6-liter gasoline V8 for 2027. It now produces 412 horsepower and 472 pound-feet of torque, giving buyers another option if they do not need the additional capability or operating characteristics of the diesel.
That matters because GM says more than 60% of heavy-duty customers choose diesel. The company already has a major share of the diesel HD market, so the new Duramax is aimed at protecting and expanding that position.
More Than an Engine Upgrade
The new diesel may be the star of the 2027 trucks, but GM has made changes throughout the chassis and control systems.
One of the most notable is the switch to rack-and-pinion electric power steering. GM calls it a segment-first application for heavy-duty pickups. The system replaces the previous hydraulic-assisted steering arrangement and is designed to provide more precise control while reducing kickback over rough surfaces.
According to GM, the electric system provides approximately 30% more steering power than the current HD hydraulic steering gear. That additional capability is intended to help with low-speed maneuvering, heavy front-axle loads, and demanding towing situations.
Electric steering also removes hydraulic pumps, hoses, and fluid from the system. GM says that can reduce mechanical complexity and steering noise while providing more consistent assistance because the system does not depend on engine speed.
Braking has also received a substantial redesign. The 2027 HD trucks use an electronic brake-boost system, which GM describes as a first for the heavy-duty pickup segment.
The new braking hardware includes larger 14.6-inch front rotors and four-piston fixed front calipers. GM says the changes are intended to increase thermal capacity and provide more consistent stopping performance when the truck is carrying or towing heavy loads.
These changes are important because more power needs to be matched by more control. Adding 555 horsepower and 1,230 pound-feet of torque would be less meaningful if the truck’s steering and braking systems were not upgraded to handle the additional capability.
Trailering technology has also been expanded. Properly equipped 2027 Silverado HD and Sierra HD models can tow up to 38,000 pounds with a gooseneck trailer. GM also lists a maximum conventional trailering capacity of 20,000 pounds on properly equipped configurations.
The trucks can be equipped with as many as 14 camera views, including Transparent Trailer View, Bed View, and Surround Vision. Trailer tire pressure and temperature monitoring is also available, along with an in-vehicle trailering application.
GM Is Still Betting Heavily on Diesel
The decision to introduce a larger diesel engine is notable because the auto industry continues moving toward electrification. GM itself has invested heavily in electric vehicles, yet its heavy-duty truck business still depends on customers who need capabilities that battery-electric pickups have not completely replaced.
Heavy-duty buyers often use their trucks for work, long-distance towing, agriculture, construction, and commercial applications. For those customers, range under load, refueling time, and maximum towing capacity remain critical considerations.
A diesel truck can be refueled quickly and can carry substantial loads over long distances without requiring the driver to plan around charging stops. That gives the new Duramax a clear role even as GM expands its electric vehicle portfolio.
Ford’s latest Super Duty diesel already delivers 500 horsepower and 1,200 pound-feet of torque in its strongest configuration. GM’s 555-horsepower and 1,230-pound-feet figures put the new Duramax above those numbers, at least on paper. The figures therefore give Chevrolet and GMC a strong answer in the ongoing heavy-duty power race.
But power numbers alone will not determine which truck is best for customers. Buyers will also consider payload, towing stability, fuel economy, reliability, pricing, service costs, and how well the truck performs under sustained loads.
GM appears to understand that point. Rather than simply installing a larger engine, it has updated the steering, brakes, transmission calibration, cooling system, and trailering technology as part of the same package.
The 2027 Silverado HD and Sierra HD are expected to reach U.S. dealers beginning late in 2026, with pricing and additional configuration details to be announced.
Its significance goes beyond the numbers printed on the specification sheet. It represents a substantial investment in internal-combustion technology at a moment when manufacturers are balancing gasoline and diesel demand against the long-term shift toward electric vehicles.
For Chevrolet and GMC, the reasoning is clear. Heavy-duty truck buyers still require vehicles that can handle demanding workloads, and many of those customers continue to prefer diesel power.
The new Duramax is GM’s response to that demand. With 555 horsepower, 1,230 pound-feet of torque, an Allison 10-speed transmission, and a redesigned chassis and control system, the 2027 HD trucks are designed to compete at the top end of the segment.
Whether these improvements provide a significant advantage will depend on how the trucks perform for customers in real-world use. For now, GM has made its position clear. The company remains committed to the diesel-powered heavy-duty truck market, with the new 8.3-liter Duramax representing a major part of that strategy.
