5.5 / 10

Buyers love rugged light-duty trucks like the Ford Raptor, Ram Rebel, and Chevrolet Silverado Trail Boss. So, it only makes sense that some companies have extended those same (or similar) packages to their heavy-duty truck lineup, too. Already there’s the Ram Power Wagon, Ford Super Duty Tremor, and Nissan Titan XD Pro-4X. And now GM has its own entry: the GMC Sierra HD AT4.

The Sierra HD AT4 (like all AT4 models) couples rugged exterior styling and off-road chops to a well-equipped cabin loaded with good optional tech. But because the Sierra’s competitors offer more in the way of safety, and because GMC has the priciest truck of the bunch (our tester costs a whopping $77,555), the HD AT4 feels like a less compelling choice in a class stacked with better alternatives.



Two things we really like about the Sierra HD: it's comically large (with the extended box, this truck measures in at 22 feet long), and the oversized grille looks like it wants to swallow up everything else on the road. And in the optional AT4 off-road trim (a hefty $14,400 add-on to the base Sierra HD), it looks rugged.

The AT4 model's massive grille gets darkened vertical chrome slats rather than the base model's bright chrome mesh. A set of 18-inch wheels with gloss black accents, wrapped in rugged all-terrain tires, replace the normal chrome set. And just below the grille, you'll find the same red tow hooks as on other AT4 models.

As for the cabin, you do get an 8.0-inch touchscreen standard (though, it looks tiny on the otherwise gargantuan vehicle) on the AT4 trim, but cheap black plastic and faux chrome surround it, just like you’ll find in the more affordable Chevrolet Silverado and light-duty Sierra. There are some nicer materials within eyeshot – like leather and soft plastic – and the black leather seats have a nice finish, but we expect better materials of a truck that costs north of $77,000. Ford and Ram are lightyears ahead in terms of material quality and design.

GMC Sierra 2500HD
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Because this truck is so massive, its cabin feels like a studio apartment on wheels. The rear bench is especially roomy, offering 39.9 inches of headroom and 43.4 inches of legroom – more than enough space for your six-foot tall author to stretch out as he might in a first-class airplane seat. The front seats offer plenty of room, too, and the 10-way power adjustability with lumbar support makes it easy to find the perfect seating position. That said, we’d prefer different leather on the seats, as it feels stiff rather than supple. And since the Sierra’s rugged personality gives it larger wheels and tires, not to mention a big diesel engine underhood, this truck is a bit loud on road.

Technology & Connectivity


Need to charge your phone? Or anything, really? This Sierra has two standard 12-volt power outlets – one up front, and one in the rear – and another 120-volt outlet in the center console. There's also a 120-volt outlet in the bed, as well as three USB ports inside and an available wireless charger directly under the infotainment screen (part of the Premium $4,215 package).

The 8.0-inch infotainment screen is small; Ram's 12-inch UConnect system trumps GMC's setup comparatively. But with the Premium package, which includes Apple CarPlay and Android Auto, a 4G LTE wifi hotspot, satellite radio, Bluetooth, and a Bose premium sound system, there's a lot of depth. And although the screen could be larger, it's laid out well, easy to use, and responds quickly to inputs.

Our tester also gets the absolutely necessary Technology package. That's a $2,125 option that adds a high-definition surround-view camera, a rear-camera mirror, a bed-view camera, a head-up display, and an 8.0-inch digital instrument cluster. For a truck this large you'll be glad you splurged on this package, especially in tight parking lots.

Performance & Handling


Powering our Sierra AT4 is the optional 6.6-liter Duramax diesel V8 (versus the standard 6.6-liter gas V8). That engine adds a hearty $9,890 onto the total asking price – but it's worth it. With 910 pound-feet of torque, the twin-turbocharged unit moves the 6,950-pound truck with relative ease. Paired with a crisp-shifting 10-speed automatic, this truck has a surprisingly nice ride. And while we didn’t do any towing during our week at the helm, knowing the Sierra 2500 AT4 can tug up to 18,500 with a traditional hitch and/or haul 3,597 pounds provides peace of mind.

Obviously, you shouldn't toss this near-7,000-pound truck into a corner expecting excellent feedback. The Sierra 2500 drives as big as it looks; the driver's seat borders on the upright positioning of a small tractor-trailer, and the steering, though functional, delivers little to no actual road feel. But it's inoffensive, if not expected in a truck this large.



We don't expect an entire active safety suite of most HD trucks, but even the GMC Sierra 2500 feels lacking. The base model doesn't even offer automatic emergency braking or forward collision alert, while both of those features (and then some) are only optional on the AT4 model. The Driver Alert II package costs $645, and along with automatic emergency braking and forward collision alert, adds lane departure warning, a following distance indicator, and automatic high-beam headlights.

Visibility is also an issue. Measuring in at 22 feet long and 6.8 feet wide, the Sierra 2500 practically forces you into the $2,125 Technology package, which adds a high-definition surround-view camera, a rear-camera mirror, a bed-view camera, a head-up display, and an 8.0-inch digital instrument cluster. This package is a must for navigating tight parking lots and driving in the city.

Fuel Economy


The EPA doesn’t have a rating for the 2020 GMC Sierra 2500. The only thing we know about the 2500’s fuel capacity is that it has a 36.0-gallon tank. So, we can’t include it in our final score.



Our GMC Sierra 2500 costs $77,555 as tested, which is a pretty hefty increase over the base Sierra HD's $37,195 starting price before options. With heavy-duty trucks getting more expensive, the Sierra is still the priciest of the bunch. The base Ford F-250 XL costs $33,705, the base Ram 2500 Tradesman costs $33,745, and the base Nissan Titan XD S costs $44,580.

Even equivalent off-road HD trucks, like the Ford Tremor ($53,390), Ram Power Wagon ($53,450), and Titan XD Pro-4X ($53,980), undercut the AT4 trim's $59,295 starting price. And most of those pickups come with more standard features and better technology.


Gallery: 2020 GMC Sierra 2500HD AT4: Review

2020 GMC Sierra 2500 AT4 Crew Cab 4x4

Engine Twin-Turbo 6.6-Liter Duramax Diesel
Output 445 Horsepower / 910 Pound-Feet
Transmission 10-Speed Automatic
Drive Type Four-Wheel Drive
Weight 6,950 Pounds
Towing 18,500 Pounds
Payload 3,597 Pounds
Seating Capacity 5
Base Price $37,195
As-Tested Price $77,555
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