A Complete Guide to Every 2027 GMC Sierra 1500 Engine, With Power and Torque Ratings

The 481-horsepower 6.6L V8 grabs the headline, but the 402-horsepower 5.7L V8 is the one that tows the most. Get that one fact straight and you’ll read the whole new engine lineup differently.

GMC officially confirmed all four powertrains on September 22, 2026, and the 2027 Sierra 1500 arrives at Valley GMC before the end of 2026. Four engines, every one of them paired to a 10-speed automatic, and every one serving a genuinely different kind of truck use. Read the chart correctly and the choice gets simple.

What’s the Plan at a Glance?

The 2027 Sierra 1500 runs four confirmed powertrains, and while two of them are brand-new sixth-generation Small Block V8s (the 5.7L and 6.6L, replacing the outgoing 5.3L and 6.2L respectively), the other two carry familiar hardware forward with a TurboMax bump and a Duramax that keeps the numbers its following was built on. So you’re looking at two fresh engines and two proven ones.

GMC lists maximum ratings when properly equipped, and capability varies by cab, bed, drivetrain, and optional packages. Read that footnote before you spec a trailer.

The Surprise: Why the 5.7L V8 Is the Towing Engine

The 5.7L V8 is the towing engine even though the 6.6L makes more power, because trailer capacity comes from axle ratios and drivetrain tuning rather than headline horsepower, and that single design choice is why the two V8s land so far apart on the chart. Look at the tow column again. The 6.6L puts up 481 horsepower and 501 lb-ft of torque, yet it caps at 9,400 lbs maximum trailering. The 5.7L produces 79 fewer horsepower and still hits 13,500 lbs. That gap matters enormously for anyone pulling a loaded landscape trailer down SR-167 every morning, or towing a boat to one of the lakes east of Auburn.

Shop the 2027 Sierra 1500 at Valley GMC to see which trim delivers the 5.7L as standard or available.

GMC frames the 6.6L as a high-displacement performance engine tuned for power output and smooth character at upper RPM ranges, not for the specific axle ratios, cooler packages, and trailer-brake integration a max-tow configuration requires. The 5.7L slots into those configurations. You see the same logic in the 305-horsepower Duramax diesel, which clears 12,100 lbs because torque delivery and drivetrain tuning do more work than peak horsepower when a trailer’s weight is behind you.

The TurboMax: More Than It Used to Be

The enhanced 2.7L TurboMax gains 40 horsepower and 25 lb-ft of torque over the outgoing version, per the official September 2026 press release, which lands it at 350 horsepower and 455 lb-ft and, oddly enough, hands it more torque than the new 5.7L V8. The torque figure is what sets it apart. The TurboMax out-torques the new 5.7L V8 (428 lb-ft) by 27 lb-ft.

Browse available Sierra 1500 configurations to see which trims pair the TurboMax as standard equipment.

The TurboMax can’t pull a heavy trailer. It caps at 9,400 lbs maximum towing, and that rules it out for the big rigs. It also tops out at a 2,310-lb payload, which is actually the highest payload in the lineup. For a contractor running a flatbed with tools and materials (not a gooseneck), or a commuter who tows a small boat on weekends and wants the best fuel economy in the gas lineup, the TurboMax makes genuine sense. It’s standard on the Pro and Elevation trims.

The Duramax Diesel: The Long-Haul Option

GMC carries the class-exclusive 3.0L Duramax Turbo-Diesel into the 2027 generation with confirmed output of 305 horsepower and 495 lb-ft of torque, and while it won’t match the 5.7L’s tow ceiling, no other half-ton competitor offers an available diesel, so for long highway miles it stands on its own. When paired with the available 34-gallon fuel tank, GMC’s GM-estimated highway range exceeds 900 miles on a single fill. Talk to our finance team about how diesel ownership fits into your total cost picture before committing.

For contractors running long stretches of I-5 or SR-18 with a loaded trailer, the diesel’s torque curve (peak torque arrives at 2,750 rpm) means the engine isn’t working as hard at highway cruising speed. The tradeoff is 12,100 lbs maximum towing, below the 5.7L V8’s ceiling, and a lower payload cap of 1,850 lbs. Diesel makes the most sense for high-mileage towers who run consistent loads in the 8,000-to-12,000-lb range.

Which Engine Fits the Green River Valley?

We can map these four engines to the buyers who walk our lot in Auburn.

The contractors and fleet operators in the valley’s industrial corridor are the ones most affected by the counterintuitive tow chart. If you’re pulling equipment or a loaded flatbed, the 5.7L is your engine. Period. The 6.6L gives you more showroom presence and more power under the accelerator, but it won’t legally tow what the 5.7L will in the same configuration.

Look first at the TurboMax if you commute SR-167 north into Kent, Renton, or Seattle and still want to tow a travel trailer or boat on the weekend. It handles lighter loads, keeps fuel cost down over a long commute, and the 2027 version is genuinely more capable than the generation it replaces.

Weekend towers with heavier rigs headed toward the Cascades, the folks pulling a fifth wheel or a larger boat, want the 5.7L or the Duramax depending on whether they’ll be doing those long highway miles regularly.

The 6.6L Denali Ultimate is for the buyer who wants the most powerful naturally aspirated half-ton V8 GMC has ever built, full stop. An impressive machine, no question. Just don’t spec it expecting to maximize your tow rating.

Value Your Trade Before the 2027 Sierra Arrives

All four engines pair to the same 10-speed automatic transmission, so shift quality and driver experience stay consistent across the lineup. The variable that decides it is what’s behind you and how many miles you put on the truck each year. Get that right and the rest follows.