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The 2027 GMC Sierra HD tows up to 38,000 lbs with a new Duramax 8.3L Turbo-Diesel V8 producing 555 hp. That is a significant jump over the 2026 model’s 36,000-lb maximum, making this the most capable Sierra HD yet. The 2027 model has not arrived at dealerships yet, but this page answers the most common questions about the upcoming truck and what shoppers can expect at Greg Hubler Buick GMC in Marion.
Two engines are offered. The standard engine is a 6.6L V8 gas unit paired with an Allison 10-speed automatic transmission. The available engine is the all-new Duramax 8.3L Turbo-Diesel V8, also paired with the Allison 10-speed automatic. Both are V8 configurations.
The new Duramax 8.3L Turbo-Diesel V8 produces 555 hp and 1,230 lb-ft of torque. These are class-leading figures for available diesel output in the heavy-duty segment.
GMC 2027 Sierra HD official specs
The Allison 10-speed automatic transmission is paired with both engine options. The Allison name carries significant weight in the work-truck world for its durability in towing and hauling applications.
The 2027 Sierra HD is the first truck in its class to use electric rack-and-pinion power steering rather than a traditional hydraulic setup. This system delivers more precise, responsive steering feel, which is particularly noticeable when maneuvering with a heavy trailer attached.
The eBoost electronic brake boost system is another segment-first on the 2027 Sierra HD. It features large front brakes and improved braking mechanics designed to provide a firm brake response on downhill grades and reduce stopping distances when trailering. Every 2027 Sierra HD includes this system as standard equipment.
Up to 38,000 lbs when properly equipped with the available Duramax 8.3L Turbo-Diesel V8. That figure represents a 2,000-lb increase over the 2026 model’s maximum. Actual tow ratings depend on configuration, trim, and equipment selected.
The Pro trim includes Adaptive Cruise Control with trailering capability, a Trailer Brake Controller, a Trailering Package, and Trailering Mirrors as standard equipment. Buyers in Marion and across Indiana who need a capable work truck from the base trim up will find the Pro already well-equipped for daily towing tasks.
The ProGrade Trailering System is an available suite that includes an In-Vehicle Trailering App. It is available on SLT and above trims. The system consolidates trailering information and controls into one interface, reducing the steps needed to monitor and adjust trailer settings while driving.
Up to 14 available camera views can be configured to assist with hitching, monitoring trailer sway, and navigating tight spaces. This multi-camera setup works alongside the ProGrade Trailering System for a more informed tow.
Yes. The Traction Select System with Tow/Haul mode is available on the Sierra HD. Tow/Haul mode adjusts transmission shift points and throttle response to suit heavy towing conditions.
Seven trims are available: Pro, SLE, SLT, AT4, AT4X, Denali, and Denali Ultimate. The lineup spans from a straightforward work-focused configuration at the Pro level to the fully loaded Denali Ultimate, which comes standard with the Duramax 8.3L Turbo-Diesel V8.
The AT4X is purpose-built for serious off-road use. It adds a factory-installed 1.5-inch suspension lift, Multimatic DSSV dampers, a rear electronic-locking differential, 35-inch Goodyear Territory MT tires, a larger steel transfer case skid plate, a front aluminum skid plate, and 16-way heated and ventilated power front seats with a massage feature. It also debuts Terrain Mode for the first time on the Sierra HD platform.
Terrain Mode adjusts shift mapping and traction control while adding automatic braking to maximize control during low-speed maneuvers on uneven surfaces. This is the first time Terrain Mode has appeared on the Sierra HD, making it an AT4X exclusive feature for 2027.
The Denali Ultimate comes standard with the Duramax 8.3L Turbo-Diesel V8 and Allison 10-speed automatic, a Signature Vader Chrome grille, exclusive 20-inch Ultra-Bright machined aluminum wheels with Gloss Black inserts, an exclusive Alpine Umber interior with full-grain leather seating, authentic Paldao wood trim, and 16-way power front seats with a massage feature.
The 2027 Sierra HD seats 6 passengers.
Three available display upgrades are offered. The 13.4-inch diagonal Premium GMC Infotainment System is the main touchscreen. The 12.3-inch diagonal digital Driver Information Center replaces the traditional gauge cluster. The 15-inch diagonal multicolor Head-Up Display projects key information onto the windshield so drivers can keep their eyes on the road and trailer.
Yes. A 12-speaker Bose Premium Series audio system is available on the 2027 Sierra HD for buyers who want a more refined in-cab listening experience.
Upper trims offer available 16-way power front seats with a massage feature, heated and ventilated perforated leather seating surfaces, heated steering wheels, authentic wood trim, and patterned aluminum accents. The AT4X includes its own exclusive 16-way heated and ventilated power front seats with massage as standard within that trim.
The 2027 Sierra HD has not arrived yet and is expected to become available in late 2026. Greg Hubler Buick GMC in Marion can provide release updates and upcoming availability information as the launch gets closer.
Not yet. The 2027 Sierra HD has not reached dealerships. Shoppers in Marion and throughout central Indiana can contact Greg Hubler Buick GMC for release updates, ordering information, and local availability as the truck gets closer to arrival.
That depends on your primary use case. The 6.6L V8 gas engine is the standard choice and suits buyers who tow frequently but want simpler fueling. The Duramax 8.3L Turbo-Diesel V8 is the right pick for maximum towing capacity at 38,000 lbs and for buyers who prioritize torque output, 1,230 lb-ft in this case, as the defining factor. If you regularly pull heavy fifth-wheel trailers or large equipment, the diesel is the clear choice.
The 2027 model introduces the all-new Duramax 8.3L Turbo-Diesel V8, a 2,000-lb increase in maximum towing capacity, segment-first electric rack-and-pinion power steering, the segment-first eBoost electronic brake boost system, and the debut of Terrain Mode on the AT4X. These are the four headline changes that separate the 2027 truck from its predecessor.
Every 2027 Sierra HD Pro includes Adaptive Cruise Control with trailering capability and the eBoost electronic brake boost system as standard. The Trailer Brake Controller also comes standard on the Pro. These systems are in place from the base trim, meaning safety and towing confidence are not reserved for upper-level packages.
The 2027 GMC Sierra HD has not arrived at Greg Hubler Buick GMC yet. The upcoming truck brings significant capability upgrades in towing, braking, steering, and diesel performance, with availability expected in late 2026. Shoppers in Marion and throughout central Indiana can contact the dealership for release updates, ordering information, and local availability as the 2027 Sierra HD gets closer to launch. Buyers who need a heavy-duty truck sooner can browse current Sierra HD inventory while comparing their options.