- Engines do the trick
- Can tow a lot
- Great assortment of camera views
- Smooth ride
- Lots of models and features
- AT4 and Denali are expensive
- No crash tests
- Forget about fuel economy
- Ponderous to drive
features & specs
The 2020 GMC Sierra tows with the best of them thanks to a strong turbodiesel and a wide variety of camera views.
The 2020 GMC Sierra HD is meant for work. It tows, it hauls, it carries passengers and cargo from one destination to the other, and it does it with a combination of brutish strength and upscale luxury. Redesigned for 2020, the Sierra HD is bigger than ever, more opulent than ever, and can haul more than ever. It also offers a series of cameras and technology tools that ease the worry of towing. We rate it a 6.8 overall for its class-leading capability, relative comfort, and many useful tech features. (Read more about how we rate cars.)
GMC’s customers told the brand they wanted a bigger, more work-oriented truck, so that’s just what GMC provided for 2020. The new Sierra HD is considerably larger than the already monstrous truck it replaces, and it offers up to 52 percent more towing capacity, which now tops out at 35,500 pounds.
The look is similar to the light-duty, 1500-series trucks, but also different. The face of the truck is much taller and more cohesive than that of the related Chevy HD trucks. The bed sides are shorter and side steps are provided in front of the rear wheels to make bed access easier.
GMC offers a choice of two engines, a new 6.6-liter, 401-horsepower gas V-8 that replaces a 6.2, and the carry-over Duramax 6.6-liter turbodiesel that grinds out 445 hp and 910 pound-feet of torque. The Duramax is hooked to a new 10-speed automatic Allison transmission that replaces a 6-speed, and a new four-wheel-drive system offers a full-time 4-High Auto setting for the first time in the Sierra HD.
Both engines are strong, but the diesel is the choice for towing, and the new 10-speed automatic helps take advantage of its power by keeping the revs in the power band more often. GMC offers up to 15 camera views to further improve towing. Otherwise, the GMC’s road manners are predictably ponderous given its size, but the ride is smoother than the competition due to an independent front suspension.
Inside, the 2020 GMC Sierra HD has room for a king in each seating position, especially in the crew cab, and its materials are upscale though not as luxurious as those in the Ram HD. The AT4 and Denali sit at the top of the lineup and offer amenities such as leather upholstery, heated and cooled front seats, heated rear seats, a heated steering wheel, OnStar telematics with a 4G LTE wi-fi hotspot, an 8.0-inch screen for infotainment with Apple CarPlay and Android Auto connectivity, a Bose audio system, and wireless device charging.
The 2020 GMC Sierra HD offers some important safety features, too. It can be ordered with front and rear park assist, GM’s rear camera mirror, blind-spot monitors, rear cross-traffic alerts, forward collision warnings with automatic emergency braking, and lane departure warnings.
2020 GMC Sierra 2500HD
The 2020 GMC Sierra strikes a commanding pose on the road.
This boy is brawny. Bigger than the 2019 model, GMC Sierra HD strikes a commanding presence with its tall, blocky grille, high hood line, integrated hood scoop, and prominent wheel flares. It’s a macho, purposeful look for a macho, purposeful truck. Inside, however, the arrangement is softer, though still functional, with more luxury as buyers move up the lineup. We give it a point for its exterior and rate it a 6 for styling.
The new Sierra HD is bigger than the truck it replaces. The wheelbase increases by about 5 inches, length by up to 11.5 inches, width by 1.4 inches, and height by up to 2 inches. The headlights sit at the top of the front end where they belong instead of halfway up like on its Chevy Silverado HD counterpart. The grille forms a large block up front that extends slightly higher than the headlights and traces the line of the forward-mounted hood scoop. The headlights have an LED light signature, and LED lighting is used for the headlights themselves, as well as the daytime running lights, taillights, and even the available fog lights and roof lights.
The lower portion of the front end is home to a bumper that incorporates those fog lights and a pair of tow hooks.
Along the sides, segmented wheel flares sit at each corner, and the doors feature flat surfaces that can easily accept stick-on signs with the names of the businesses of the contractors who drive these trucks. The sides tuck in at the bottom, and faint character lines suggest haunches over the front and rear wheels. Side steps in front of the rear wheels and bed steps at each corner of the rear bumper allow access to the bed, which sits an inch lower this year. Like its light-duty trucks, GMC has made the bed wider this year to create the most bed volume in the class. A new Carbon Fiber Pro bed made of, you guessed it, carbon fiber, is a class exclusive that GMC promises is more durable than steel or aluminum.
Another class exclusive (shared with Chevrolet) is the MultiPro tailgate that can act as a bed step, a workbench, or a spot to sit, and even offers built in speakers for (literal) tailgating.
Inside, the design is a mix of upscale cues and truck-like functionality. Large dials, buttons, and switches work well with gloves, while soft-touch surfaces and occasional bits of contrast stitching borrow from luxury cars.
2020 GMC Sierra 2500HD
The GMC Sierra HD’s powerful engines and relatively smooth ride are strengths; handling is not.
GMC concentrated its efforts on improving towing capability for 2020 and the efforts have paid off. The base gas V-8 is more powerful, towing capacity is up by as much as 52%, and a series of camera views helps drivers monitor their loads. The Sierra HD also rides well for a large truck, though handling is predictably plodding. We rate a 6 for performance.
The 2020 GMC Sierra HD can tow up to 35,500 pounds with a fifth-wheel, up from 23,300 pounds for the last-generation truck. That puts it at the front of the class. When towing on a hitch, it can haul up to 20,000 pounds. The top towing figures are achieved with the available diesel engine and dual rear wheels.
The turbodiesel is the Duramax 6.6-liter V-8 that makes 445 hp and 910 lb-ft of torque. It isn’t updated for 2020, but its transmission is. GMC switches from a 6- to a 10-speed automatic transmission made by Allison. GMC says in tow/haul mode it can send all 910 lb-ft of torque to the ground in first gear. That allows this massive truck to accelerate from 0-60 mph in 7.4 seconds.
Unladen, the diesel provides a strong punch of acceleration that drops off as the rpms and speeds rise. The new 10-speed shifts smoothly and keeps the engine in its power band more often. The diesel is also very strong when towing a trailer, and doesn’t seem overly taxed, even when heading uphill at 6,000 feet above sea level during our test in Wyoming.
The gas engine is a new 6.6-liter V-8 that cranks out 401 hp and 464 lb-ft of torque, figures that are up by 41 and 84, respectively, versus the outgoing 6.2-liter V-8. The gas engine doesn’t have the torque of the diesel, but it is the payload leader and will work well for those who don’t need to tow bigger loads. It is teamed with a 6-speed automatic.
The Sierra can also haul 7,442 pounds of payload in the duallie and 4,534 pounds with single rear wheels. Both figures are competitive but not best in class.
GMC offers up to eight cameras to provide 15 camera views to make trailering far easier. A hitch view helps the driver back the truck up to a trailer, a split side view shows where the trailer is in its lane and biases to the side of a turn when the signals are used, and the very unique transparent trailer view stitches together multiple camera views to show the position of a trailer while also allowing the driver to see through it. The latter requires an accessory camera mounted to the back of the trailer.
Not only does the camera system aid towing, but the Sierra HD also comes standard with trailer sway control and a trailer brake, and the diesel adds an exhaust brake. It’s rocksteady when towing.
Like other HD pickups, the Sierra HD is large and ponderous on the road. However, its road manners are better than its competitors thanks to an independent front axle, digital variable assist steering with road crown compensation and variable ratios that speed up at low speeds, and overall comfortable tuning.
2020 GMC Sierra 2500HD
Comfort & Quality
It’s not as special inside as the Ram HD, but the 2020 Sierra HD combines upscale ambience with lots of space.
Space is not a problem in the 2020 GMC Sierra HD pickups, especially in the crew cab models that will fit the starting lineup of a basketball team. While the upscale models offer plenty of soft-touch surfaces, they can’t match the Ram HD pickups for overall quality. We award the Sierra HD extra points for passenger and cargo space, as well as a point for interior quality.
GMC Sierra HD buyers said they wanted their trucks big, and GMC obliged with added interior space and bigger road presence. The front seats are wide and there is 10-gallon-hat head room. The rear seat in the crew cab has ample head, leg, and shoulder room.
The cab has a large center console and room for storage below the rear seats. The bed is wider than that of the competition to make it easier to carry four-by-eight sheets of plywood and drywall. GMC makes access to the bed easier with its MultiPro tailgate that can act as a step and side steps in front of the rear wheels. Unfortunately, it bangs on the trailer hitch of trucks so equipped. Inside the bed, the Sierra HD has 12 corner tie-downs and a 120-volt power outlet. Very functional.
Light-duty, and now heavy-duty, trucks have moved upmarket in interior quality and amenities. GMC, with its Denali and new AT4 trim levels, takes advantage of that new market, and makes an attempt to rival luxury cars. With the prices these trucks can command, they should feel special inside. The Ram HD does, but the GMC is simply nice rather than luxurious. The truck features soft-touch surfaces on the dash, doors panels, and center console. It has some subtle contrast stitching on the seats and dash, but it lacks the flourishes of the Ram 1500, as well as the huge center touchscreen.
2020 GMC Sierra 2500HD
The 2020 Sierra HD offers a variety of safety features but hasn’t been crash tested yet.
Neither of the agencies that crash test vehicles, the IIHS nor the NHTSA, has tested the 2020 Sierra HD. Without crash-test data, we can’t rate the Sierra HD for safety.
The Sierra HD’s many available cameras make towing easier and safer. The truck is also offered with front and rear park assist and GM’s rear camera mirror, as well as such active safety features as blind-spot monitors, rear cross-traffic alerts, forward collision warnings with automatic emergency braking, and lane departure warnings. These active safety features work with GM’s safety alert seat that vibrates in the direction of a potential danger.
We’ll update this report if the Sierra HD is crash-tested.
2020 GMC Sierra 2500HD
The GMC Sierra HD has a truck to get the work done and offers a bevy of unique features to ease the process.
The 2020 GMC Sierra HD comes in a variety of models that offer more and more capability. Buyers can opt for anything from base work truck trims up to luxurious AT4 and Denali models. Numerous options and accessories are also offered, and GMC’s killer app is a class-leading 15 camera views that make towing easier. We rate the GMC Sierra HD a 7 for features.
GMC offers the Sierra HD in 2500 and 3500 models, each in base, SLE, SLT, AT4, and Denali trim levels. The 3500 comes with single or dual rear wheels, and every model is offered with rear- or four-wheel drive that this year adds a full-time, 4-High Auto mode. The trucks are available in regular, double, and crew cab body styles, and two bed lengths are offered: 6-feet-7 inches and 8-feet-2 inches.
The $41,595 base model is a work truck with vinyl floors and manual locks and windows.
While fewer buyers choose a mid-range model, we recommend evaluating a mid-range SLE or SLT model based on the equipment you need without jacking up the price.
The AT4, which starts at $59,295, and Denali, which runs $65,295 in its base version, sit at the top of the lineup and take a different approach to luxury. The AT4 goes with black trim bits, an off-road suspension, skid plates, and knobbier tires, while the Denali has a chrome look, a more street-oriented approach, and even more luxuries.
Standard and available features on the AT4 and Denali models include leather upholstery, dual-zone automatic climate control, 10-way power adjustable front seats, heated front and rear seats, cooled front seats, a heated steering wheel, the Pro Grade Trailering system with several cameras, satellite radio, remote starting, OnStar telematics with a 4G LTE wi-fi hotspot, an 8.0-inch touchscreen for infotainment with Apple CarPlay and Android Auto connectivity, a Bose audio system, wireless device charging, GM’s Multi-Pro tailgate that drops down in several positions, and 18- (AT4) or 20-inch (Denali) alloy wheels.
Notable options include a rear camera mirror, a suite of active safety features, a gooseneck fifth-wheel towing package, and GMC’s new Carbon Pro carbon-fiber bed.
2020 GMC Sierra 2500HD
Without EPA fuel economy ratings, we can’t rate the 2020 GMC Sierra HD, though fuel economy is not a strength.
As a heavy-duty pickup, the 2020 GMC Sierra HD isn’t rated for fuel economy. Without government ratings, we can’t provide our own rating.
Fuel economy may play a role in why buyers choose the diesel engine. It will be more efficient than the gas engine, especially for towing. The price premium on the diesel likely won’t ever be recouped at the pump, but the diesel also offers better power for towing and around town.
More frequently nowadays, people choose HD trucks as daily transportation. That’s good reason to institute government fuel economy ratings for these trucks.