GMC's popular Denali sub-brand has made it into the Heavy Duty truck segment. Like the full-size 1500 below it in the lineup, the 2024 GMC Sierra 2500 HD is now available with an ultra-luxurious Denali Ultimate trim. It offers various upgrades over the regular Denali trim, including a standard V8 turbo diesel engine, a more upscale interior with massage seats, a premium sound system, and a few model-specific exterior bits and pieces. GMC didn't just focus on the extras with this truck, though, because it's also made various changes under the hood to improve the low-end torque and towing capacity across the lineup.

As standard, the Sierra 2500 HD comes with a 6.6-liter gasoline V8, but GMC offers the 6.6-liter Duramax diesel V8 as optional on every trim. The turbo diesel mill delivers 470 horsepower and 975 lb-ft of torque, which outguns the Ram Cummins Turbo Diesel inline-six on power and torque; Ford's Power Stroke diesel engine in the F-250 Super Duty outperforms the GMC, though, with 475 hp and 1,050 lb-ft of torque.

Despite not having the best specifications on paper, there is a lot to love about this truck and its powertrain. We think it might be the most well-rounded HD truck on the market.

Styling: Macho Lux

GMC facelifted the entire Sierra HD lineup for the 2024 model year, with each trim getting its own unique grille, fascia, finishes, and personality. The Denali Ultimate sits at the top of the lineup, expanding on the already flashy Denali trim using darker materials on the exterior. All eyes will gravitate towards the grille, partially because it's eye-level for many people, but mostly because of its cool Vader Chrome finish and blacked-out GMC logo. If Darth Vader wanted to tow a horse trailer, this is likely the truck he would use.

Other unique touches on the Denali Ultimate include 20-inch Ultra-Bright machined aluminum wheels with black accents and an 'Ultimate' fender badge with the topography of Mount Denali, the highest mountain peak in North America. The badge also lets onlookers know that you have the torque-rich Duramax diesel engine paired with a ten-speed Allison automatic transmission.

In just a week behind the wheel, we learned that truck diehards absolutely love how the Sierra HD Denali Ultimate looks. While GMC offers Regular Cab, Double Cab, and Crew Cab styles, the Denali Ultimate is only available as a Crew Cab.

Powertrain: World-Devouring Torque

Lesser Sierra HD trims come standard with a 6.6-liter gasoline V8 producing 401 horsepower and 464 lb-ft of torque (unchanged from last year), now routed to a standard 10-speed automatic transmission. This V8 delivers more power and torque than the standard 6.8-liter V8 in the Ford F-250, and more torque than the 6.4-liter V8 in the Ram 2500.

Optional on all trims for around $9,500 (depending on configuration), but standard on the Denali Ultimate, is the 6.6-liter Duramax turbo diesel V8. It now produces 470 hp and 975 lb-ft (up from 445 hp and 910 lb-ft) thanks to a more efficient turbocharger, improved engine braking from the turbo vane actuator and valve springs, new cylinder heads with improved cooling jackets, and higher-flow injectors with more injection pressure. GMC would never quote a 0-60 mph time for such a vehicle, but we managed to get this massive truck up to speed in around six seconds, which is incredibly impressive for its size and weight.

Towing is the far more likely application for this engine, and it doesn't disappoint in that area. The capacity changes a bit depending on cab style, but the Sierra 2500 HD can pull up to 22,500 pounds when equipped with a Max Towing Package (21,900 lbs in Crew Cab guise). The GMC can out-tow the Ram 2500, but the Ford F-250 edges it out with a 23,000-pound max capacity.

Driving Impressions: Fire Up That Diesel

Driving a Heavy Duty truck is typically a lesson in discomfort, as suspensions that are built to pull objects that weigh as much as a house require a sacrifice in ride quality. Since we didn't need to tow anything during our week with the Sierra HD, we had ample time to experience the truck as a daily driver. Obvious size impediments aside, the Sierra HD is reasonably comfortable on a long trip, never jolting occupants with an overly bouncy ride. That being said, we'd still prefer to commute in a Sierra 1500 if we didn't need the towing capability of the 2500.

Acceleration from the Duramax diesel is tremendous, especially with the recent improvements to the low-end torque for 2024. The 10-speed automatic is perfectly calibrated to the engine, executing smooth and deliberate gear changes exactly when we wanted them. This is easily the best transmission tuning in the segment, as we've come to expect from GM trucks. The steering is light enough to make tight parking maneuvers manageable and accurate enough to keep the truck in its lane on the highway, but we still look forward to the day when GMC can put Super Cruise hands-free driving on an HD truck.

Interior: Log Cabin Luxury

Prior to this 2024 facelift, GMC's Heavy Duty truck lagged behind the competition in terms of interior quality. GMC still offers a Sierra HD with a barebones cabin featuring vinyl seats, a simple seven-inch touchscreen, and analog gauges for customers who want a work truck. That's not what you get inside the Denali Ultimate. This truck is decked out with a new 13.4-inch infotainment system and 12.3-inch gauge cluster display, a 15-inch head-up display, 12-speaker Bose audio system with stainless steel speaker grilles, and 16-way power massage seats with luxurious Alpine Umber full grain leather and Paldao wood.

Pretty much every modern amenity you could want is found in this trim, except for a panoramic moonroof, which is available on the Ford Super Duty. We love GMC's Google-based infotainment system, which offers wireless CarPlay and Android Auto as well as Google voice commands that respond more accurately to your requests. This is easily the best cabin GMC has put together for a Heavy Duty truck.

Practicality: A Flexible Package

Truck owners who rarely carry two or more passengers will be fine with the Regular Cab and Double Cab Sierra HD, but the Crew Cab is the best way to transport people comfortably. It offers an impressive 43.4 inches of legroom in the back seat compared to just 35.2 inches in the Double Cab and none in the Regular Cab. The Regular Cab is only available with the 98.27-inch Long Bed option, while the other two body styles can also be equipped with a shorter 82.25-inch Standard Bed.

All trims from SLE and above now get GMC's MultiPro tailgate with multiple positions depending on different use cases. It can fold into a much-needed bed step or act as a bed stop for longer items. There's even a built-in Kicker Bluetooth speaker to make tailgate parties, job sites, or camping trips more enjoyable.

Verdict: The Ultimate Luxury Tow Rig

It's possible to take home a base Regular Cab Sierra 2500 HD Pro model with the gas V8 for around $45k, but the price can quickly balloon from there. The top Denali Ultimate trim with the standard Crew Cab body style and Duramax diesel engine starts at $91,900, making it more expensive than the Ram 2500 Limited but less than the Ford F-250 Limited. Is it worth it? Absolutely.

Trucks like these are so similar in performance that the purchase decision typically boils down to brand loyalty rather than a specific tow rating or payload capacity. GMC made major updates to its Sierra HD lineup for 2024, improving the range from bottom to top, culminating with the Denali Ultimate. The market for nearly six-figure tow rigs is niche, but we could easily see well-off horse, boat, or race car owners gravitating to this truck. If you have the cash and a heavy thing to pull behind it, we'd highly recommend the Sierra 2500 HD Denali Ultimate.