Under The 2027 GMC Sierra's Hood: Four Engines, 10-Speeds StandardAutoGuide.comCraig ColeTue, September 22, 2026 at 5:22 PM UTCAdd us on Googleunder the 2027 gmc sierra s hood four engines 10 speeds standardDETROIT- We just got our first hands-on look at the 2027 GMC Sierra 1500.As expected for an overhauled vehicle, this tough truck wears updated – and handsome – exterior styling, the cabin has been totally overhauled, and there's more technology than ever before, but there's also huge powertrain news.Behind that prominent grille, a range of engines is available in the new Sierra. Giving drivers plenty of choice, GMC is offering four different options for the 2027 model year, including two brand-new V8s.Hands-On Preview: 2027 GMC Sierra 1500 Offers More Without ExtraHands-On Preview: 2027 GMC Sierra 1500 Offers More Without ExtraDETROIT - GMC just took the wrapper off its redesigned 2025 Sierra 1500, and we just got our first – and very quick – look at this significantly updated pickup. This truck wears handsome new sheet metal; the interior has been completely overhauled, and there's huge news under the hood, including not one but two fresh V8 engines. Plus, there's plenty of exciting technology as well.Craig ColeCraig Coleunder the 2027 gmc sierra s hood four engines 10 speeds standardThe Powertrain BookendsAs before, the standard offering is a 2.7-liter TurboMax four cylinder, though there's nothing "entry-level" about this unit's output. Expect a whopping 350 horsepower from this force-fed four-cylinder along with a peak of 455 pound-feet of torque.AdvertisementAdvertisementThose are staggering figures for an engine of such modest displacement, plus they easily beat the 2027 Ford F-150's base 3.0-liter EcoBoost V6, which is rated at 325 hp and an even 400 lb-ft of torque. When the new Sierra is fitted with a TurboMax engine, expect the standard tow rating to be 9,400 pounds.At the opposite end of the powertrain spectrum is GM's lovely 3.0-liter Duramax straight-six diesel. Smooth, impressively quiet and super-efficient, this turbocharged oil-burner delivers a more-than-respectable 305 hp with a whopping 495 lb-ft of torque, more twist than all but the 2027 Sierra's biggest V8. With diesel fury under the hood, this truck should be able to drag up to 12,100 pounds when properly equipped.2027 GMC Sierra 1500: All The Details2027 GMC Sierra 1500: All The DetailsView Gallery75 photosLegendary Engine Displacement Revived for 2027Sandwiched between the TurboMax four-cylinder and the Duramax diesel are two new V8s. These sixth-generation powerplants replace GM's outgoing 5.3- and 6.2-liter engines that have a somewhat tarnished reputation, particularly the 6.2, of which hundreds of thousands have been recalled because major components in the rotating assembly are out of spec.AdvertisementAdvertisementRegardless, the smaller of these new V8s now displaces 5.7 liters, a historically significant figure that equates to 350 cubic inches, the same as Chevrolet's famed small-block V8 that was produced by the millions for many decades. A far cry from its ancestor, this new 5.7 is rated at a healthy 402 hp and 428 lb-ft, impressive figures that give this V8 an edge over the 2026 Ram 1500 with the 5.7-liter Hemi as well as the 2026 F-150 with the quad-cam 5.0-liter Coyote V8. The former competitor is rated at 395 horses and 410 lb-ft, while the latter is rated at an estimated 400 and 410, respectively.Expect a 2027 Sierra with the 5.7-liter engine to be able to tow up to 13,500 pounds.Finally, the flagship engine in this new GMC is a 6.6-liter V8. Expect a staggering 481 hp and 501 lb-ft of torque from this hulking engine. To top those figures, you have to step up to Ford's and Ram's up-level turbocharged offerings. The F-150's high-output, non-hybrid 3.5-liter EcoBoost V6 delivers up to 510 lb-ft of twist, but it's only good for 450 hp. In high-output form, the Ram's 3.0-liter Hurricane straight-six has a horsepower edge, delivering 540 ponies, though its torque advantage is modest, topping out at 521 lb-ft.All told, a Sierra with the 6.6-liter V8 should offer 9,400 pounds of standard towing capacity.under the 2027 gmc sierra s hood four engines 10 speeds standardThese V8s have larger displacement and a few technological tweaks, including higher compression ratios, upsized throttle bodies, and reworked intake manifolds, but they retain their classic pushrod design with two valves per cylinder. GM has used this tried-and-true design for decades to great effect. There is also variable valve timing on both engines, plus they feature port and direct fuel injection for enhanced performance and efficiency in all driving conditions.AdvertisementAdvertisementDigging a little deeper, the 5.7-liter V8 is slightly undersquare, with a bore of 3.78 inches (96 mm) and a stroke of 3.86 in. (98 mm). In contrast, the 6.6 is oversquare, maintaining its sibling's stroke but pairing it with a 4.06-in (103.3-mm) bore. It should be no surprise, but both engines feature weight-saving aluminum blocks and cylinder heads.under the 2027 gmc sierra s hood four engines 10 speeds standardThe 10-Speed Is Now StandardThe other big news for the 2027 model year is the Sierra's transmission. GMC has finally jettisoned its old eight-speed automatic, which was paired with the base engine, meaning their 10-ratio gearbox is standard across the powertrain lineup. This should deliver enhanced performance and efficiency, making the most of the TurboMax engine's already impressive output.The redesigned Sierra will also be available with a 34-gallon fuel tank. Final economy figures have not yet been released, but this should provide impressive driving range regardless of the engine, though good luck being able to fill up with today's gas and diesel prices.Coming SoonThe 2027 GMC Sierra 1500 is expected to go on sale late this year, which means pretty soon, since the months are rapidly dwindling and fall is officially here. Official pricing, fuel economy estimates, and other details about this truck have not yet been shared, but stay tuned for all those details.AdvertisementAdvertisementBecome an AutoGuide insider. Get the latest from the automotive world first by subscribing to our newsletterhere.