The heavy-duty pickup truck roaming North America like an overfed deer has no antlers, but scraping against a tree or two with a GMC Sierra 2500HD or 3500HD probably won’t hurt too much either. Built to power the world, the heavy-duty Sierras are offered with either a 401-hp 6.6-liter V-8 and six-speed automatic transmission or a 445-hp 6.6-liter V-8 Duramax Diesel with 910 pound-feet of torque. The latter gets a 10-speed automatic and is the powertrain of choice for the Sierra 3500 if you plan on making the most of 20,000 pounds of conventional towing capability. Let’s see the deer try it. If that sounds like too much of a truck, the half-ton Sierra 1500, reviewed separately, is a great alternative. The Sierra comes with lots of trailer assist technology and even an optional multifunction tailgate, but it falls a bit short on newer competitors like the Ford Super Duty and Ram HD. The difference between the GMC and Chevy’s Silverado HD is almost entirely visual, but the bow tie alternative does offer a more affordable entry into the mega-truck-dom.
What’s New in 2023?
The heavy-duty GMC Sierra 2500HD and 3500HD are not receiving dramatic equipment changes for 2023. That’s because GMC will be announcing a mid-cycle refresh for the Sierra HD 2024 that includes more power, torque and towing capacity.
Price and Where to Buy
We’ll start with the crew cabin and opt for a standard bed in the Sierra 2500HD. We’d avoid the rugged AT4 model and the chrome-laden Denali model despite its upgraded appearance. Instead, we recommend opting for the SLT trim level and adding four-wheel drive and a V-8 diesel. SLT comes standard with GMC’s Versatile MultiPro tailgate, heated steering wheel, heated front seats, power adjustable front seats and remote start. It also opens up more options than the lower SLE trim. We will opt for the SLT Comfort package which includes ventilated cushioned front bucket seats, heated rear seats and sliding rear windows. The Driver Alert package is also worth adding as it makes the giant easier to live with thanks to aids like blind spot monitoring, lane departure alerts, and front and rear parking sensors.
Engine, Transmission and Performance
The Sierra HD comes standard with a gas-powered 6.6-liter V-8 engine that produces 401 horsepower and 464 pound-feet of torque. It is paired with a six-speed automatic transmission and rear or four-wheel drive. The optional Duramax diesel 6.6-liter V-8 produces 445 horses and 910 pound-feet of lap mountain haul, and works via an Allison 10-speed automatic. You can also specify single or dual rear axle (the iconic “dual”). Even though we only drive the diesel variant, we do it gas combustion powertrain sample mechanically identical Chevy Silverado 2500HD and appreciate his submissive behavior. However, there’s no denying that the Duramax/Allison combination is a highlight of the heavy-duty Sierra, and a no-brainer for those who regularly pull heavy loads. The engine is very smooth, and the transmission is very responsive. Together they help The 2500HD Denali we tested achieves impressively fast acceleration time. The giant GMC also has a pleasant ride quality for its kind. While steering is unclear at highway speeds, the Sierra still feels more agile than its heavy-duty competitors. The trail-ready AT4 model is a tougher model on a generally chrome-filled rig, with off-road suspension and a locking rear differential to go with the dark aesthetic.
Towing and Payload Capacity
The strongest Sierra 3500HD can carry 7442 pounds in its cargo bed and tow as much as 35,500 pounds with a gooseneck trailer. However, such a large capacity requires a diesel engine, a regular cab, rear-wheel drive and dual rear axle. The Sierra 2500HD is only offered with a single rear axle, and its most powerful version is good for 3979 pounds of payload and 18,500 pounds of towing. The maximum conventional towing for a diesel powertrain is 20,000 pounds.
Real World Fuel Economy and MPG
Since EPA not testing vehicles as heavy as the Sierra HD and its giant competitors, we can only rate their real-world mpg on our highway fuel-efficient routes. We only tested the Sierra 2500HD Denali with a diesel engine, which produces 17 mpg on the highway. By comparison, the diesel powered Silverado 2500 LTZ crew cab and the regular Ram 2500 Tradesmen cabin diesel we tested both delivered 19 mpg. Those sticking to the standard GMC gas-fed V-8 should expect to see worse fuel economy than the diesel option.
Interior, Comfort and Cargo
Inside, the Sierra 2500HD and 3500HD have large dashboards that house user-friendly switchgear. Most models have a folding front bench that can be replaced with a pair of bucket seats and a full center console. The Sierra interior can also be selected with a heads-up display, heated steering wheel, heated and cooled front seats, and wireless charging. Unfortunately, the cabin panels fit snugly and the material quality is mediocre. While there are plenty of soft-touch surfaces, and most models benefit from durable plastic, the top-of-the-line Denali is sorely short on its luxury bill. The most luxurious alternative to the Ram houses the GMC in large part thanks to a much more luxurious look and feel. However, the Sierra HD will please pickup truck buyers who prioritize practicality and versatility. Along with ample passenger space in the crew cabin, the GMC is filled with practical interior storage space. The standard and long cargo box has built-in ladders on either side of the bed and the rear bumper has it at every corner. The box is further customizable with LED lighting, movable straps, and a 120-volt outlet. Sierra’s biggest exhibition of heavy duty is innovative multi-function tailgate, which has six different positions that include a work surface and a bench. This is a tailgater’s dream come true.
Infotainment and Connectivity
Each Sierra HD has a standard touchscreen infotainment system with Apple CarPlay and Android Auto. While the base models have fewer options, they can still be equipped with a 120-volt outlet and a mobile hotspot. Most trim levels have an 8.0-inch screen and an additional charging port. All systems include a set of easy-to-access rotary knobs and physical buttons. The larger touchscreen can be upgraded with built-in navigation, a Bose audio system, SiriusXM satellite radio and a rear seat entertainment system. GMC also offers a smartphone app that can be used to remotely control trailer functions. Likewise, the truck’s infotainment system allows users to save different trailer profiles to monitor maintenance.
Safety Features and Driver Assistance
While the truck can be equipped with various driver assistance technology, none of which are standard, and arch-rivals offer more assists. However, GMC does have a comprehensive camera system featuring up to 15 different viewing modes, including a “transparent” mode that allows users to virtually see through the attached trailer as if they weren’t there. For more information on Sierra HD crash test results, visit the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) website. Key security features include:
- Front collision warning and automatic emergency braking available
- Blind-spot monitoring and rear traffic warning available
- Departure line available
Warranty and Maintenance Coverage
GMC provides a competitive warranty package that matches the coverage provided by competitors Ford and Ram, but, unlike these alternatives, GMC includes one free scheduled maintenance visit.
- Limited warranty covers three years or 36,000 miles
- Powertrain warranty covers five years or 60,000 miles
- Free maintenance is covered for the first year
2020 GMC Sierra 2500 Denali 4WD Crew Cabin
front engine, rear 4 wheel drive, 5 passengers, 4 door pickup
PRICE ACCORDING TO TEST
$78,455 (base price: $65,295)
turbocharged and intercooled 32-valve V-8 diesel pushrod, iron block and aluminum head, direct fuel injection
403 cu in, 6599 cc
445 hp @ 2800 rpm
910 lb-ft @ 1600 rpm
10 speed auto
Suspension (F/R): control arm/solid axle
Brakes (F/R): 14.0-in/14.1-in ventilated disc
Tires: Goodyear Wrangler Trail Runner A/T, LT275/65R-20 126/123S M+S
Wheelbase: 158.9 inches
Length: 250.1 inch
Width: 81.9 inches
Height: 79.8 inches
Passenger volume: 139 cu ft
Curb weight: 8260 lb
Launch, 1 ft: 0.3 sec
60 mph: 6.5 seconds
90 mph: 14.4 seconds
Rolling start, 5–60 mph: 7.7 sec
Top gear, 30–50 mph: 3.7 sec
Top gear, 50–70 mph: 5.0 sec
-miles: 15.0 seconds @ 92 mph
Top speed (limited by governor): 98 mph
Braking, 70–0 mph: 207 feet
Road grip, 300 ft diameter skidpad: 0.73 g
Observed: 12 mpg
Driving on the highway 75-mph: 17 mpg
Highway coverage: 610 miles
EPA FUEL ECONOMY
Combined/city/highway: not rated
More Features and Specifications