The 2027 Chevrolet Silverado 2500HD and 3500HD, along with their GMC Sierra HD counterparts, are reportedly set to receive two new engines for the 2027 model year. The changes would bring new gas and diesel V8 powertrains to GM’s heavy-duty trucks while the current generation remains in production.
New Gas V8 Reportedly Coming for 2027
According to GM Authority, citing sources within the automaker, both engines currently offered in the Silverado and Sierra HD are expected to be replaced for 2027.
The current 6.6-liter gasoline V8, known by the L8S code, is reportedly being replaced by an L8T V8 with the same displacement. For 2026, the existing engine produces 401 horsepower and 464 pound-feet of torque.
The report expects those figures to increase, potentially helping GM compete more closely with Ford’s 7.3-liter “Godzilla” V8, which produces 430 hp and 485 lb-ft.
Despite sharing its displacement with the sixth-generation, aluminum-block V8 used in the Silverado and Sierra 1500, the L8T is expected to retain the predecessor’s robust iron construction. The engine is also expected to prioritize low-end torque and towing performance rather than exceeding 500 hp.
The projected output for the HD gas trucks is around 450 hp and 500 lb-ft.
Duramax Diesel Also Set for an Update
Diesel buyers are also reportedly in line for an updated powertrain. An ordering guide revealed by Jones Chevrolet in Wisconsin indicates that the 2027 Sierra and Silverado HD will receive changes to their optional Duramax turbodiesel V8.
The corresponding engine order code is expected to change from L5P to L6P. The ordering guide does not specify the diesel’s displacement, leaving open the possibility that GM is considering a larger Duramax engine to match or surpass the output of competing Ford and Ram powertrains.
The L5P first appeared in the 2017 Silverado HD and Sierra HD. When introduced, it produced 445 hp and 910 lb-ft. A higher-pressure fuel system increased those figures in 2024 to 470 hp and 975 lb-ft.
Those numbers remain below the Ram Heavy Duty’s 6.7-liter Cummins, which produces 1,075 lb-ft, and the Ford Super Duty’s 6.7-liter Power Stroke, which produces either 1,050 or 1,200 lb-ft depending on the state of tune.
The report suggests the L6P would need to produce at least 1,100 lb-ft to compete in the heavy-duty truck segment.
Why GM Could Introduce the Engines Before a Redesign
Automakers typically introduce new powertrains alongside major vehicle redesigns, but GM has previously updated its heavy-duty trucks between generations and even between facelifts.
The 2017 Silverado and Sierra HD, for example, received the L5P engine in 2017, three years before the trucks’ planned 2020 redesign. The reason for that strategy is unknown, but it allows customers to receive updated engine technology without waiting for a complete truck redesign.
HD Redesign Reportedly Coming Later
While the redesigned light-duty Silverado and similarly new Sierra are due later this year, their heavy-duty counterparts are expected to remain on the current generation until 2029.
Along with revised sheetmetal and new interiors, the HD trucks are expected to receive more towing and payload capacity, improved active safety, and additional technology aimed at helping owners complete work more efficiently.
For 2027, however, the reported focus is on new gasoline and diesel V8 powertrains arriving before the heavy-duty trucks receive their next major redesign.
