The 2027 Silverado HD and GMC Sierra HD are reportedly in line for new gasoline and diesel engines, even though the heavy-duty pickups are not expected to receive the full redesign planned for their light-duty counterparts.
New Engines Reportedly Coming to HD Trucks
GM Authority, citing sources familiar with the matter, reported that the two heavy-duty trucks will offer engines designated L8S and L6P.
The L8S is described as an updated version of the current 6.6-liter L8T naturally aspirated gasoline V8. The L6P would replace the current 6.6-liter L5P Duramax turbodiesel V8.
Diesel Engine Could Gain Displacement
Output figures have not been disclosed. However, GM Authority reported that the L8S will retain the same 6.6-liter displacement, while the L6P could receive a displacement increase.
A larger displacement could help improve performance over the current L5P, which produces 470 horsepower and 975 lb-ft of torque. That would put the engine in a stronger position on paper against heavy-duty rivals from Ram and Ford, whose available Cummins and Power Stroke diesel engines exceed 1,000 lb-ft of torque.
The current L8T gasoline V8 produces 401 horsepower and 464 lb-ft of torque. Both engines are paired with a 10-speed automatic transmission, after gas models dropped their 6-speed automatic for the 2024 model year.
GM Has Not Confirmed the Powertrain Changes
General Motors has not confirmed the reported powertrain updates. Order books for the 2027 Silverado HD are reportedly scheduled to open on September 17, while production is reportedly set to begin this November.
Those dates could bring additional details about the reported engine changes.
Light-Duty Silverado and Sierra Also Get New Engines
Separately, the new engines coming to the light-duty Chevrolet Silverado and GMC Sierra have been confirmed. They include an updated TurboMax and two new Gen 6 small-block V8s that will replace the 5.3-liter L84 and 6.2-liter L87.
The 6.2-liter L87 has been at the center of a recall and proposed class-action litigation involving connecting rod, crankshaft and bearing failures.
Meanwhile, the 3.0-liter Duramax inline-six turbodiesel is expected to be largely carried over, reportedly retaining its current output of 305 horsepower and 495 lb-ft of torque.
Comprehensive specifications for the 2027 Silverado 1500 are reportedly due on September 17, alongside the reported opening of 2027 Silverado HD order books.
