GM has decided to refresh its heavy-duty pickup lineup with changes to the powertrain, steering, braking, chassis controls, and trailering systems. The biggest change is the introduction of a completely new 8.3L Duramax Turbo-Diesel V8, paired with an improved 6.6L gas V8. The changes will apply to the current Chevrolet Silverado HD and GMC Sierra HD, with US deliveries starting in late 2026.
What’s new about the 8.3L Duramax V8?
The new 8.3L Duramax Turbo-Diesel V8 is GM’s first in-house-developed, clean-sheet HD diesel engine, designed specifically for pickup trucks. It delivers 555 HP and 1,668 Nm of torque.
This engine will use a compacted graphite iron cylinder block, forged crankshaft and connecting rods, and steel pistons. The forced induction system will comprise a variable-geometry turbocharger and a two-stage air-to-water charge-cooling system. GM has also revamped the cooling and combustion system to handle high-load operations, including towing.
This diesel is equipped with an Allison 10-speed automatic transmission and an upgraded exhaust brake system. GM will produce this engine at its DMAX manufacturing plant in Brookville, Ohio.
What changes have been made to the gasoline engine?
The 6.6L V8 standard gasoline engine has also been revamped. Now this engine delivers 412 BHP and 640 Nm of torque.
The improvements include a redesigned Turbo-Jet intake manifold, an updated lubrication system, an engine oil cooler, and a digital oil level gauge.
The 6.6L Gas V8 and the 8.3L Duramax diesel both feature the Allison 10-speed automatic transmission. Both engines have updated shift programming designed to keep engine speed ideal during acceleration, hill climbs, and towing.
What has been changed regarding steering and braking?
The 2027 HD trucks will get the rack-and-pinion Electric Power Steering. It replaces the existing hydraulic power steering and, according to GM, it offers around 30% more steering torque than the current hydraulic version.
Steering assist also no longer depends on engine speed or the braking-assist function. GM has incorporated various steering calibrations for drive modes, but the system eliminates hydraulic pumps, lines, and steering fluid.
Brake boost is also electronic, and the trucks get bigger front rotors measuring 14.6 inches in diameter, four-piston fixed front callipers, and revised rear brake parts. The braking system is paired with driver-assistance technologies like Adaptive Cruise Control and Automatic Emergency Braking.
How will the drive modes and towing systems work in the new model year?
2027 HD models will feature revamped Normal, Tow/Haul and Off-Road driving modes with coordinated powertrain, steering, brakes and chassis parameters. The ZR2 and AT4X versions will get an updated Terrain Mode that allows single-pedal off-road performance in 4HI and 4LO.
Towing capacity will stand at 17,236 Kilogrammes in properly equipped versions, while the maximum GCWR will be 21,092 Kilogrammes. Towing features will include up to 14 camera views, Transparent Trailer View, Bed View, Surround Vision, trailer tyre pressure/temperature monitoring, and Trailer Side Blind Zone Alert.
When can you expect 2027 HD models to be released?
The 2027 Chevrolet Silverado HD and GMC Sierra HD will be available at U.S. dealerships starting in late 2026. No information is available yet on MSRP or specific configurations. Pricing, trims, and other specifications will be revealed later.
