The 2027 Chevy Silverado HD and GMC Sierra HD Debut a Gigantic 8.3L Diesel Engine Called Mongoose

2026/09/24

Categories: auto

A blue pickup truck towing an off-road vehicle trailer on a dirt road surrounded by mountains and greenery.

General Motors

The new massive-displacement Duramax diesel will serve as an optional engine on both the Silverado HD and Sierra HD. As the new flagship engine, the Mongoose produces 555 horsepower and 1230 pound-feet of torque. It’ll be joined by an updated gas-slurping 6.6-liter V-8, which now generates 412 horses and 472 pound-feet. The gasser benefits from a new turbo-jet intake manifold that GM tuned specifically for HD performance. This powertrain also receives better cooling and lubrication under load, which is helpful since these HD pickups are often towing something. Both engine options are connected to an Allison 10-speed automatic transmission.

Of course, the new trucks don’t get power increases for nothing. Towing figures are up too. Naturally. The HD’s maximums have risen to 20,000 pounds with a conventional trailer hitch, while models equipped with a gooseneck setup can now lug up to 38,000 pounds. Every diesel truck configured with a dual-rear-axle setup can now tow at least 30,000 pounds. While the 2500 maxes out at 23,200 pounds, opting for the crew cab drops that figure to 22,400.

Dark green pickup truck parked on rocky terrain with blue sky and distant mountains in the background.

General Motors

The new trucks should also feel better behind the wheel. GM has finally ditched the old recirculating-ball steering found on every other heavy-duty truck and switched to an electrically assisted rack-and-pinion setup. Not only does the new system have about 30 percent more power than the outgoing hydraulic setup, according to GM, but it should offer much more precise steering. The first-in-the-segment steering is joined by a first-in-the-segment electronic brake-boost system.

Speaking of stopping power, the new GM trucks come with 14.6-inch front rotors, four-piston front calipers, and updated hardware for the rear brakes. The new brakes can take more heat and—coupled with a new pedal placement and more linear brake travel—should improve confidence while hauling heavy loads.

GM says the new 2027 Chevy Silverado HD and 2027 GMC Sierra HD trucks are expected to arrive by the end of the year. Pricing hasn’t yet been announced, but we shouldn’t have to wait too long, considering that the new year is quickly approaching.


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Headshot of Jack Fitzgerald

Jack Fitzgerald’s love for cars stems from his as yet unshakable addiction to Formula 1.
After a brief stint as a detailer for a local dealership group in college, he knew he needed a more permanent way to drive all the new cars he couldn’t afford and decided to pursue a career in auto writing. By hounding his college professors at the University of Wisconsin-Milwaukee, he was able to travel Wisconsin seeking out stories in the auto world before landing his dream job at Car and Driver. His new goal is to delay the inevitable demise of his 2010 Volkswagen Golf.

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