General Motors is giving its heavy-duty pickup trucks a major powertrain upgrade for the 2027 model year, introducing an all-new 8.3-liter Duramax turbo-diesel V8, available for the Chevrolet Silverado HD and GMC Sierra HD.According to a press release by GM, the new engine is the brand's first clean-sheet heavy-duty diesel V8 designed, developed and manufactured in-house specifically for heavy-duty pickup applications. It produces 555 horsepower and 1,230 lb-ft of torque, which GM says are best-in-class figures for diesel engines in the segment. The powertrain is designed around the demands of towing and hauling, with a compacted graphite iron cylinder block, fully forged crankshaft and connecting rods, and steel pistons.GM has also equipped the Duramax with a dual-stage air-to-water charge-cooling system and a variable-geometry turbocharger. An updated cooling strategy is intended to maintain consistent performance when the trucks are working hard. The engine is paired with an Allison 10-speed automatic transmission, while the package also includes upgraded exhaust braking and a new aftertreatment layout designed to support long-distance towing and regeneration.The new diesel is only part of GM's changes for its 2027 heavy-duty lineup. The existing 6.6-liter gasoline V8 has also been enhanced and now produces 412 horsepower and 472 lb-ft of torque. Both engines use the Allison 10-speed transmission with revised shift logic to help maintain an appropriate operating range under different driving and towing conditions.GM is also introducing a segment-first rack-and-pinion electric power steering system for its HD trucks. The system replaces the previous hydraulic-assisted setup and provides approximately 30% more power than the current hydraulic steering gear. The trucks also receive a new electronic brake-boost system, larger 14.6-inch front rotors, and four-piston fixed front calipers.For off-road driving, the lineup adds an available Terrain Mode on ZR2 and AT4X models. In 4HI and 4LO, it allows one-pedal operation by automatically applying the brakes when the driver lifts off the accelerator. For towing, GM says properly equipped trucks can pull up to 20,000 pounds with a conventional hitch and up to 38,000 pounds with a gooseneck. The maximum available gross combined weight rating (GCWR) reaches 46,500 pounds.The 2027 Chevrolet Silverado HD and GMC Sierra HD are expected to reach U.S. dealers beginning in late 2026. GM has not yet announced pricing or additional product details. Future updates will announce the MSRP and additional product information.
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