GM reveals 2027 Silverado HD and Sierra HD with 8.3-liter dieselQuartzCris TolomiaFri, September 25, 2026 at 11:42 AM UTCAdd us on GoogleGM is revealing refreshed heavy-duty Silverado and Sierra trucks with a new 8.3-liter diesel hero imageGeneral Motors unveiled updates to its 2027 heavy-duty truck lineup on Thursday, introducing the refreshed Chevrolet Silverado HD and GMC Sierra HD with a new 8.3-liter Duramax turbo-diesel V8 engine, segment-first electric rack-and-pinion steering, and a new electronic brake-boost system.The new diesel engine, which GM is calling Mongoose, produces 555 horsepower and 1,230 pound-feet of torque, the company said. The optional powerplant is paired with an Allison 10-speed automatic transmission. The updated standard 6.6-liter gas V8 now produces 412 horsepower and 472 pound-feet of torque and is also matched to the Allison 10-speed.Maximum towing capacity on the refreshed trucks rises to 20,000 pounds with a conventional hitch and up to 38,000 pounds on models equipped with a gooseneck setup, GM said. Diesel models riding on a dual-rear-axle configuration are capable of pulling a minimum of 30,000 pounds, according to Car and Driver.AdvertisementAdvertisementThe 8.3-liter engine is GM's first clean-sheet heavy-duty diesel designed, developed, and manufactured in-house for pickup applications, the company said. It will be built at GM's DMAX facility in Brookville, Ohio, a 1.4-million-square-foot plant. GM previously invested $920 million to expand the facility."This new diesel engine is the culmination of decades of GM diesel development and integration," Norman Peralta, GM's executive chief engineer of global engine and battery systems, said in a statement.According to Car and Driver, the electric rack-and-pinion system brings roughly 30 percent more power to bear compared with its hydraulic predecessor, and it ditches the recirculating-ball steering geometry that remains standard on rival heavy-duty trucks. Up front, the braking hardware consists of 14.6-inch rotors clamped by four-piston calipers. GM also added an updated drive-mode strategy with a new Terrain Mode featuring one-pedal off-road control, a first for GM HD trucks.GM says both trucks are slated to reach dealerships before year's end, though the company has not yet disclosed what customers will pay for them.AdvertisementAdvertisementGM teased the Mongoose engine earlier this week, confirming its displacement and name but providing no output figures at that time. The Mongoose name is a reference to Ford's 6.7-liter Power Stroke diesel, whose internal development codename is Scorpion. Ford's Power Stroke produces 500 horsepower and 1,200 pound-feet of torque, and Ram's competing 6.7-liter Cummins inline-six is rated at 430 horsepower and 1,075 pound-feet.GM said more than 60 percent of heavy-duty truck customers opt for a diesel engine. The company already holds the majority of diesel share in the segment. The refresh comes as GM has faced broader sales pressure: Silverado sales fell 7.7% in the second quarter, contributing to a 4.2% overall U.S. sales decline for that period, though GM said it still expects to have gained market share in the full-size truck segment.