L8S V8 Could Replace The Silverado HD’s L8T For 2027

The L8S V8 could be the biggest change coming to the heavy-duty Silverado and Sierra for the 2027 model year. GM Authority reports, citing sources within the automaker, that the Chevrolet Silverado 2500HD and 3500HD will trade their current 6.6-liter gasoline engine for this new powerplant. The GMC Sierra HD equivalents are slated for the same update. However, nothing is official until GM confirms the details.

What The L8S V8 Replaces

The engine on its way out carries the codename L8T, and it displaces 6.6 liters, just like its replacement. In the 2026 Silverado 2500HD, the L8T produces 401 horsepower at 5,200 rpm and 464 lb./ft. of torque at 4,000 RPM. The base truck pairs it with an Allison 10-speed automatic. However, those numbers are presumed to rise so the new V8 can better compete with Ford’s 7.3-liter “Godzilla” V8. That engine makes 430 horsepower and 485 lb./ft.

The pressure to keep up is real, because the three-quarter-ton and one-ton pickup segments are incredibly competitive, and every horsepower counts. GM has not matched its rivals on the spec chart for a few years. A bump in output from the new engine would help change that for the heavy-duty gas trucks.

Iron Construction And Expected Output

The L8S V8 shares its displacement with the sixth-generation, aluminum-block V8 found in the Silverado and Sierra 1500. However, it is expected to keep the robust iron construction of its predecessor. Because of that, it probably will not crest the 500 horsepower expected from the smaller trucks’ optional 6.6-liter V8. Instead, it should be tuned for greater low-end torque and towing performance.

In practical terms, plan on around 450 horsepower and 500 lb./ft. for the heavy-duty gas trucks. Those figures would top the Godzilla’s 430 horsepower and 485 lb./ft. Still, they remain educated guesses until GM releases official specifications.

Why The L8S V8 Is Arriving Early

Automakers typically wait for a major redesign before introducing a new powertrain. However, the L8S V8 is reportedly arriving during the current generation of heavy-duty trucks. The redesigned light-duty Silverado and similarly new Sierra are due later this year, but their heavy-duty siblings will have to wait until 2029.

This is not a new move for GM, which has a history of updating its heavy-duty trucks between generations and even between facelifts. For example, the ’17 Silverado and Sierra HD received a new engine three years before their planned 2020 redesign. Why the automaker does this is unknown. Even so, customers should not complain if it means they get the latest engine technology sooner.

For now, the L8S V8 looks like a solid reason to keep an eye on the ’27 Silverado HD and Sierra HD. We hope to learn more about the new gas engine soon, since GM has not shared the official numbers yet.