2027 Chevy Silverado HD and GMC Sierra HD Revealed With GM's Insane New 8.3L Duramax Diesel V8

Electronic brakes and electric power steering also fortify the new Chevy Silverado HD and GMC Sierra HD pickup trucks

written by Greg Migliore
edited by Steven Ewing
9/24/2026
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What's new: GM is launching an all-new Duramax diesel for heavy-duty trucks.
Why it matters: The lucrative work truck business is core to GM, and these trucks were in need of an upgrade.
Edmunds says: An all-new diesel is the most important upgrade for a work truck. GM's are now at the forefront.

For a quarter of a century, General Motors and its heavy-duty truck owners have relied on the muscular Duramax V8 diesel engine to get stuff done. It's the cornerstone of GM's work truck business and its loyal owners drive those diesels into the ground. For 2027, the Duramax is getting a complete makeover as the centerpiece of the refreshed Chevrolet Silverado and GMC Sierra heavy-duty trucks.

This engine is dubbed "Mongoose" for a pretty funny reason. Basically, mongooses eat scorpions, and "Scorpion" is the nickname of Ford's heavy-duty Power Stroke diesel engine. GM's all-new Duramax turbodiesel V8 measures 8.3 liters and generates 555 horsepower and a whopping 1,230 lb-ft of torque. The outgoing Duramax V8 made 470 hp and 975 lb-ft, so this is a healthy increase. This will allow the Silverado HD and Sierra HD to tow up to 38,000 pounds with a gooseneck trailer.

"We brought the hammer," Ken Morris, GM's senior vice president of global product safety, integration and motorsports, said during a media event in Pontiac, Michigan.

More than 70% of heavy-duty owners tow each month, and many tow more than 4,000 miles per year. Heavy-duty vehicles aren't vanity trucks used for commuting.

"When it comes to our HD customers, good isn't enough," Morris said. "They demand absolute confidence."

An all-new diesel for work

The new V8 diesel is a clean-sheet design developed by GM. It has a graphite iron cylinder block, a fully forged crankshaft, connecting rods and steel pistons. GM launched the Duramax engines in partnership with Isuzu in 2001, but GM has handled all Duramax engineering in-house since 2010.

Engineers say the engine will have a broad torque curve for towing, hauling and climbing challenging inclines. The new design will also reduce noise, vibration and harshness. It teams with a 10-speed automatic transmission and has improved exhaust braking.

GM will build the new heavy-duty diesel engine at an expanded factory in Brookville, Ohio.

GM will also continue to offer the heavy-duty trucks with a 6.6-liter V8 gasoline V8 making 412 hp and 472 lb-ft. This is a different 6.6-liter V8 than the new engine used in GM's light-duty trucks. That said, more than 60% of heavy-duty customers choose a diesel engine for their truck.

More than just an engine update

GM upgraded the steering and brake systems for its new heavy-duty trucks. The automaker added an electric rack-and-pinion power steering setup, tuned for a more precise feeling, less kickback, and a quieter drive with better on-center feel. The automaker claims this is a segment-first technology and it replaces the hydraulic-assisted steering system. The steering is fortified for front-axle loads, low-speed maneuvers and towing. By cutting out hydraulic components like pumps, hoses and fluids, GM hopes to reduce maintenance costs.

GM says the new electronic brake boost system is the first of its kind in the heavy-duty space. The system has larger 14.6-inch front rotors and four-piston calipers that should reduce pedal travel. The brakes provide greater stopping power and a more linear, predictable feel, said Glenn Babiak, GM's chief engineer for heavy-duty trucks.

GM also updated the trucks' drive modes, including the tow/haul mode and off-road settings. The suspension systems largely carry over but have been retuned for better ride and handling character. GM left the sheetmetal and interiors unchanged, as has been its past practice, with a refresh likely coming in the next couple of years.

Beefed up for off-roading

GM also fortified the off-road versions of its big trucks. The Silverado ZR2 and Sierra AT4X are lifted 2.5 inches (1 inch for the 35-inch Goodyear tires and 1.5 inches for the suspension) and come with Multimatic dampers and a new Terrain mode. GM also tuned the steering to have better feedback for when its rigs encounter obstacles, like rocks, to allow the driver to get less of a kickback through the steering wheel.

GM also added a feature in four-wheel-drive mode that applies the brakes when lifting off the throttle during off-roading, a first for its heavy duties.

Despite the trucks' large dimensions, heavy-duty owners often use them for ranching or farm work and they live in remote areas. GM tested the vehicles in places like Moab, Utah, and the Mojave Desert to prove their prowess in challenging situations.

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by Greg Migliore

Greg Migliore is an accomplished journalist with more than two decades covering the auto industry. He was the editor-in-chief of Autoblog for more than seven years and also served as the editorial director of AutoGuide. He's also been an editor at Automobile and Autoweek magazines. A widely quoted industry expert, he has contributed commentary to Autoline After Hours, NPR, Yahoo Finance and America on the Road. He's a graduate of Eastern Michigan University, Michigan State University and the Yale Publishing Course. He is a member of the North American Car, Truck and Utility Vehicle of the Year Awards jury. When not writing, editing or driving the latest new vehicles, Greg can be seen driving around in his extremely low-mileage 2006 Dodge Charger.

edited by Steven Ewing

Steven Ewing is Edmunds' director of editorial content. An automotive journalist for more than half of his life, Ewing's been on staff at Winding Road magazine, Autoblog, Motor1.com, CNET, and he was the U.S. correspondent for Top Gear magazine. He's also contributed to publications like Automobile magazine, Car and Driver, The Drive, Jalopnik, Porsche Panorama, and more. Ewing has worked in the automotive industry since 2003. From testing prototype cars in the Arctic Circle to spilling a beer on a Formula 1 driver at the 24 Hours of Le Mans (oops), he's always got an interesting story to tell.

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