The 2020 GMC Sierra HD has the muscle to tow 30,000 pounds

With all-new trucks, big and small, from Ford, Ram, Chevy, GMC, and even Jeep, America’s pickup truck war continues to intensify. Pickup buyers have a larger selection of trucks to sift through than ever before, and now they can add the new larger and more capable 2020 GMC Sierra Heavy Duty to their shopping list.

The Sierra is GMC’s best-selling model, and it’s an important part of GM’s $65 billion truck business. The all-new light duty version of the GMC Sierra reached dealers last August, and now the Sierra HD receives much of the hardware and technology found in its smaller brother. Hardware and technology, says Duncan Aldred, the Vice President of GMC Global, “will give it a maximum towing capacity way in excess of 30,000 pounds.”

“The all-new 2020 Sierra HD is the most capable heavy-duty truck that we’ve ever offered,” Aldred says. “It’s the crown jewel of GMC.”

Of course, the Sierra HD has always been larger than the light-duty version, but now it absolutely dwarfs the Sierra 1500. Park the two side by side and the light duty truck looks like one of those toy trucks kids can drive at Disneyland. The new Sierra 2500 is 10 inches longer and 2 inches taller than its processor. GMC has also stretched its wheelbase 5 inches and widened its cab an inch, giving it the same cab width as the 1500 model.

2020 GMC Sierra 2500HD camper side profile
2020 GMC Sierra 2500HD GM

GMC says the truck now has class-leading front head and legroom in crew cab models, and it has 3 inches more rear-seat legroom than the current model. This is even more significant when you consider that 90 percent of Sierra HD buyers chose the crew cab body style and the 6.6-liter Duramax turbo diesel V-8 engine.

Surprisingly, GMC hasn’t squeezed any more power from the popular engine. Its ratings remain 445 hp at 2800 rpm and 910 lb-ft of torque at 1600 rpm. However, it’s now mated to an all-new 10-speed Allison automatic transmission, which has closer gear spacing than the outgoing Allison six-speed automatic for improved performance and efficiency. Like the Duramax engine, it will also be shared with Chevy’s Heavy Duty Silverado models and will have a Tow/Haul mode.

Like Chevy, GMC will also offer an all-new gasoline V-8 in the Sierra HD, but it refused to give us any details on that powertrain, which will be announced in a couple of weeks.

The truck rides on a completely new architecture, also shared with the Chevy Silverado HD. (Fortunately the Sierra HD doesn’t share its styling with the Chevy.) “Weight reduction wasn’t a huge priority,” says Jaclyn McQuaid, the chief engineer on the Sierra HD. “Trailering is the most important consideration for Sierra Heavy Duty customers, so we concentrated on the truck’s towing capability. We gave it a beefier driveline and suspension, a stiffer frame, larger axles and propshafts and an enhanced cooling system.”

2020 GMC Sierra 2500HD rear 3/4 mountain
2020 GMC Sierra 2500HD GM
2020 GMC Sierra 2500HD side step
2020 GMC Sierra 2500HD GM

2020 GMC Sierra 2500HD interior driver
2020 GMC Sierra 2500HD GM
2020 GMC Sierra 2500HD 3/4 front atvs
2020 GMC Sierra 2500HD GM

GMC also better integrated the Diesel Exhaust Fluid tank into the frame so it’s no longer hanging down under the cab like an afterthought. (That was a major complaint from customers.) And it moved the DEF filler neck from under the hood to behind the fuel filler door, where it’s found on Fords and Rams.

GMC’s ProGrade Trailering System, which debuted on its light duty truck last year, is also available. It offers 15 unique camera views, including what GMC calls a “transparent trailer view.” This feature uses the tailgate-mounted camera and an available accessory camera mounted on the rear of the trailer to basically eliminate the trailer from the driver’s view.

Other interesting tech offered on the Sierra HD is a rear camera mirror, which GM has used in Cadillacs and some SUVs, and a head-up display that even includes an inclinometer display for the road grade. Pretty cool. Oddly, GM is still not offering adaptive cruise control on its trucks.

McQuaid, who has spent the last 20 years at GM, mostly in the truck space, also pointed out that the truck’s bed rails are an inch lower than before to aid the loading and unloading of cargo. There are also steps built into the bed-sides and the corners of the rear bumper, and the truck features the GMC’s MultiPro six-function tailgate that debuted on the light-duty truck.

2020 GMC Sierra HD transparent trailer
2020 GMC Sierra HD GM
2020 GMC Sierra 2500HD foldting tailgate 2 step
2020 GMC Sierra 2500HD GM

The tailgate’s aren’t interchangeable, however. “It looks the same and functions the same as the tailgate on the 1500,” says Matt Noone, director of GMC exterior design. “However, it’s an all-new piece created specifically for the HD truck.” GMC says the new Sierra HD has class-leading cargo bed volume. Unlike the Ford, which is aluminum bodied, the Sierra’s cab and bed continue to be made of steel.

Other exterior bits worth buzzing about are the larger hood scoop on diesel models and the truck’s new elevated hoodline, which instigated raising the driver’s seat about an inch for greater visibility. There are four yellow running lights on the roof for the full Peterbilt affect at night and orange side markers with the GMC logo embedded in the plastic at the top of each wheel-well flare. Unfortunately there’s still an old-school, whip-style antenna sticking up out of the right front fender like it’s 1985.

GMC introduced its more luxurious Denali trim level back in 1999 on the Yukon and added it to the Sierra two years later. Last year 29 percent of all GMCs sold were Denalis, up from 19 percent back in 2013, and 54 percent of the 2019 Sierras sold are equipped with the top-of-the-line trim level.

Named for the highest point in North America, Denali is a 20,310 foot summit in Alaska’s Denali National Park. It’s also the highest trim level on the 2020 GMC Sierra 2500 and 3500 HD models. It includes premium leather with large-pebbled grain and contrasting stitching, authentic open-pore wood, and dark-finish aluminum trim. Although the Sierra uses the same seat frames as the Silverado, the seat padding and upholstery is unique to each truck.

2020 GMC Sierra 2500HD Duramax badge
2020 GMC Sierra 2500HD GM
2020 GMC Sierra 2500HD interior passenger brown
2020 GMC Sierra 2500HD GM

2020 GMC Sierra 2500HD pulling camper
2020 GMC Sierra 2500HD GM

On the outside is a Denali exclusive grille so large and so chrome it could double as a full-size bedroom mirror and, of course, Denali special 20-inch chrome wheels. The Sierra 2500 HD displayed at the truck’s reveal rode on Goodyear Wrangler TrailRunner AT tires, size 275/55R20, while a 3500 Dually Denali sat on Michelin Primacy XC rubber.

New to the Sierra HD is the AT4 trim level, which debuted on the 2019 light duty truck and has proved to be a hot seller. Although it’s not exactly competition for the Ford Raptor, the Sierra AT4 HD is more off-road ready than other Sierra models. The trim level adds Rancho shocks, skid plates, an Eaton locking rear differential, and 18-inch wheels with Michelin all-terrain tires. The truck’s Traction Select System also gets a specific Off-Road Mode. Hill Descent Control and Hill Start Assist are standard.

Visually the AT4 is set apart with a dark chrome grille and body color bumpers and grille surround. There are also red recovery hooks and dark interior trim. AT4 is embroidered in the headrests and the all-weather floor mats.

It’s a good time to be in the market for a big bad pickup. This reveal of the 2020 GMC Sierra HD comes soon after the unveiling of the Silverado HD and the new Ram Heavy Duty, the latter of which just premiered at the Detroit Auto Show with 1000 lb-ft of torque. Throw in the hot-selling Ford Super Duty, which was recently redesigned in 2017, and there’s never been a better time to buy a new tow rig.

Click below for more about
Read next Up next: ’80s and ’90s cars gain major momentum at Arizona auctions
Your daily pit stop for automotive news.

Sign up to receive our Daily Driver newsletter

Subject to Hagerty's Privacy Policy and Terms of Conditions

Thanks for signing up.

Leave a Reply

Your email address will not be published. Required fields are marked *