GM Duramax 8.3L V8 Brings 555 Horsepower to 2027 HD Trucks

• GM’s new Duramax 8.3L Turbo-Diesel V8 produces 555 horsepower and 1,230 lb.-ft. of torque in the 2027 Chevrolet Silverado HD and GMC Sierra HD, with properly equipped trucks rated to pull up to 38,000 pounds on a gooseneck trailer.
• Both trucks switch from hydraulic to electric power steering and gain a first-ever electronic brake-boost system for heavy-duty pickups, changes GM says sharpen control at low speeds and under load.
• The updated 2027 Silverado HD and Sierra HD reach US dealers in late 2026; GM has not released pricing.

A New Engine Built Around Towing, Not Just Numbers

General Motors has redesigned the powertrain, steering and brakes on its heavy-duty pickups for the 2027 model year, and the centerpiece is a diesel engine built entirely in-house for the first time. The Duramax 8.3L Turbo-Diesel V8 lands in the Chevrolet Silverado HD and GMC Sierra HD with 555 horsepower and 1,230 lb.-ft. of torque, numbers GM says lead the segment among diesel-powered heavy-duty trucks.

Over 60 percent of heavy-duty truck buyers choose a diesel engine, and GM already holds the largest share of that market. The new engine gives the company a reason to defend that lead: a compacted graphite iron block, forged crankshaft, forged connecting rods and steel pistons form the core of an architecture GM designed specifically for heavy-duty pickup use rather than adapting from a lighter-duty application.

A dual-stage air-to-water charge cooling system and a variable-geometry turbocharger keep the engine breathing under sustained load, the kind of demand a truck faces climbing a mountain grade with a loaded trailer for twenty minutes at a time. GM pairs the diesel with an Allison 10-speed automatic transmission, upgraded exhaust braking and a new aftertreatment system built around long-distance towing rather than short daily commutes.

Buyers who skip the diesel get a reworked gas engine too. The standard 6.6L gas V8 now makes 412 horsepower and 472 lb.-ft. of torque, figures GM says lead every other 2027 heavy-duty gas engine. A new Turbo-Jet intake manifold, revised lubrication system and an engine-mounted oil cooler support the higher output.

Trailering numbers climb alongside the horsepower. Properly equipped trucks reach up to 46,500 pounds gross combined rating (GCWR), with a maximum of 38,000 pounds on a gooseneck trailer and 20,000 pounds on a conventional hitch. Every diesel dually model can tow at least 30,000 pounds.

Electric Steering Replaces Hydraulics for the First Time in the Segment

The bigger change for daily driving sits in the steering column. GM has dropped the hydraulic power steering pump that heavy-duty trucks have used for decades and replaced it with a rack-and-pinion electric system, a first for the segment. The company says the new setup produces roughly 30 percent more steering assist than the outgoing hydraulic gear, a difference that counts most at low speed with a loaded front axle or a plow mounted up front.

Removing the hydraulic pump, hoses and fluid cuts a source of leaks and maintenance that owners of older heavy-duty trucks know well. GM also says the electric system reduces kickback on rough roads and trims noise. It no longer shares a hydraulic circuit with the brakes, so engineers tuned steering and braking as separate systems instead of a compromise between the two.

Braking gets its own overhaul. The 2027 Silverado HD and Sierra HD switch to an electronic brake-boost system, another heavy-duty pickup first, with larger 14.6-inch front rotors and new four-piston front calipers. GM says the changes shorten pedal travel and produce a more consistent pedal feel when a loaded trailer pushes back on the truck on a downhill stop. The electronic system also feeds data to driver-assistance features like adaptive cruise control and automatic emergency braking, and GM says it can flag signs of brake fade or a fluid leak earlier than the outgoing hydraulic setup.

Four Drive Modes, Including a New One-Pedal Off-Road Setting

GM expanded its drive-mode lineup so the engine, steering, brakes and chassis respond together rather than independently. Normal mode covers commuting and unloaded driving. Tow/Haul adjusts shift points, exhaust braking, steering assist and brake-boost tuning for a loaded trailer. Off-Road loosens the traction and stability control to allow more wheel slip on dirt or gravel.

The new addition is Terrain Mode, available on the off-road-focused ZR2 and AT4X trims, which brings one-pedal control to 4HI and 4LO. Lift off the accelerator and the truck applies its own braking, a feature meant to help drivers hold a steady pace down a steep, technical grade without riding the brake pedal.

For owners who tow regularly, GM added camera views the previous generation lacked, including Transparent Trailer View and Bed View, on top of the existing Surround Vision system, for a combined 14 available camera angles. An in-vehicle trailering app, Trailer Side Blind Zone Alert and trailer tire pressure and temperature monitoring round out the setup, aimed at drivers hitching up a large fifth-wheel or gooseneck trailer without a spotter.

When the Updated Trucks Arrive, and What They Cost

GM builds the new diesel at its expanded DMAX plant in Brookville, Ohio, a 1.4 million-square-foot facility the company spent $920 million upgrading to handle the engine at high volume. The updated gas V8 continues to come from GM’s Tonawanda plant in New York.

The 2027 Chevrolet Silverado HD and GMC Sierra HD reach US dealers in late 2026. GM has not yet released pricing or trim-level details for the diesel engine option, and the company says more product information will follow closer to launch. Buyers cross-shopping the segment will want to watch for those numbers against Ford’s Super Duty and the Ram Heavy Duty lineup, both of which have leaned on diesel torque and towing figures to compete for the same commercial and enthusiast buyers GM is chasing here.