Make no mistake, this truck is huge.
Heavy-duty trucks are special-purpose tools designed to tow immense loads and haul mountains of stuff in all kinds of conditions. Like other HD pickups, the 2021 GMC Sierra 2500 AT4’s general lack of refinement, low fuel efficiency and ponderous dynamics make living with it day to day a challenge if you don’t need the vast capability it offers.
LikeTowing and hauling capabilityRefined powertrainIngenious tailgate
Don’t LikeLackluster performanceSame old interiorBrash styling
Providing a bit of extra style and off-road capability, the Sierra 2500 AT4 models feature dark chrome exterior accents, body-color bumpers and a bold grille design. The standard bright-red recovery hooks look great and should be super useful on the trail. Ensuring this truck can take you out into the wilderness, it comes with Rancho shocks, a locking rear differential and standard 18-inch wheels with Michelin all-terrain tires, though this example rolls on swanky 20-inch rims.
Bigger isn’t always better
With a crew-cab body and off-road suspension, this Sierra is enormous, about a trailer hitch short of 21 feet in length, and that’s with just the 82-inch, standard-length bed. Its elevated cab gives you skyscraper views of surrounding traffic and makes climbing onboard a chore. Excluding the gargantuan telescopic towing mirrors, its body is no wider than a GMC Sierra or Chevy Silverado 1500’s, but this thing feels like it takes up a lane and a half, a sensation that’s accentuated by its almost comically raised hood that partly obscures forward visibility and frightens pets and small children.
Maneuverability is a challenge with this truck. Parking can be stressful, and I instinctively swing wide for every turn to avoid clipping curbs or scraping other vehicles. The Sierra 2500 isn’t really any bigger than rival heavy-duty pickups from Ford and Ram, but it sure feels a size or two larger.
Helping make things a little more manageable, GMC offers a range of useful technologies. The available ProGrade Trailering system, for instance, provides up to 15 different camera views. This includes a neat transparent-trailer feature that uses video to make it look like there’s nothing behind the truck. A rear camera mirror is also offered, which displays real-time video on a screen mounted underneath the rear-view mirror glass, providing a much wider field of view.
For folks who regularly tow, this truck offers loads of clever features that can make it much less stressful. A clever automatic electric parking brake keeps the truck from rolling that small amount when you shift into park, something that can make hooking up a trailer quite frustrating. The towing mirrors can extend or retract at the push of a button, hill-start assist and hill-descent control help keep loads safe and secure when traversing mountainous terrain, and tow/haul mode will even remain engaged at the next key cycle so you don’t have to manually turn it on again. This is all great stuff, but perhaps the Sierra’s cleverest feature is actually its simplest one.
20-inch wheels look downright tiny on this big truck.
By the numbers
So you always know exactly what your particular truck is rated to tow or haul, GMC includes a sticker on the door jamb that spells everything out, like the gross vehicle weight rating, maximum payload, conventional trailering capacity, curb weight and more. This takes the guesswork out of how much you can safely handle.
Flexing its muscles, this Sierra 2500’s maximum payload rating is 3,232 pounds and it can tow up to 14,500 pounds with the hitch. Hook a gooseneck trailer up instead, and that figure increases to an impressive 16,620 pounds.
One more number of note: six. That’s how many functions the Sierra’s available MultiPro Tailgate offers. This is one of the most innovative pickup truck features to come out in the last 20 years. This ingenious setup has what amounts to a small gate within the main tailgate, which lets you haul freight more securely, easily reach items stored in the bed and it even works as a step so you can conveniently climb into the cargo box.
The MultiPro Tailgate is one of the Sierra’s most innovative features.
Modest performance, immodest consumption
The Sierra 2500’s standard 6.6-liter gasoline V8 is potent sounding and smooth running, but even with the truck bed empty and no trailer in tow it feels overmatched. Despite having direct fuel injection and even variable valve timing, this engine just doesn’t seem to perform like something with 401 horsepower and 464 pound-feet of torque should. It’s not particularly punchy around town, and merging onto the highway takes longer than expected, the silky and astute six-speed automatic transmission doing its best to help get this rig up to speed. I blame the Sierra’s towering body, mammoth frontal area and ready-for-action weight of 7,418 pounds for this pokey performance. Drivers who need more capability and confidence (or just want to roll some coal) can get a 6.6-liter Duramax diesel matched with a 10-speed gearbox, though you pay through the nose for the privilege of burning oil. This powertrain adds about 10 grand to the truck’s price tag.
Since the Sierra 2500’s gross vehicle weight rating is greater than 8,500 pounds, it’s exempt from fuel-economy testing. Still, unladen, in real-world driving, I’ve averaged around 14 miles per gallon according to the trip computer, which isn’t too terrible for something of this size and weight.
The truck’s ride is definitely on the firm side, but it’s not so starchy that it crashes over bumps or shatters your spine. The ride is a touch harsher than I’d like, but this stiffness is necessary so you’re not sitting on the bump stops when the bed’s full of cargo. Load this GMC up with bricks, gravel or a cord or two of firewood and I bet it would ride damn near like a Lexus. The Sierra’s steering is slow and imprecise, plus it’s prone to let the truck wander a bit, but the independent front suspension gives it an edge over competing heavy-duty trucks, which still come with solid front axles.
This interior is dull and drab.
Giant truck, tiny screens
GM’s current-generation pickups are not known for their stellar interiors. Silverado and Sierra cabins in both light- and heavy-duty form are low-budget affairs made of unattractive hard plastic. The seats are flat, and many of the secondary controls are of low quality. Ram has a clear advantage in this area and even Ford’s older trucks are a hair nicer.
The Sierra AT4’s infotainment system with integrated navigation is easy to use and responsive, but it’s displayed on an 8-inch touchscreen that looks tiny on such an expansive dashboard. Further cheapening the experience, this panel’s viewing angles are not great, with the colors easily washing out.
The $7,975 AT4 Premium Package includes a range of amenities such as Apple CarPlay and Android Auto that both connect wirelessly, rear cross-traffic alert, front and rear parking sensors and automatic high beams. It also gets you a clear and crisp head-up display and GMC’s Safety Alert Seat, which vibrates to warn the driver of danger.
The Sierra HD is one tough truck.
Comfort in this truck is mixed. The 10-way power-adjustable driver’s chair is firm but nearly free of any bolstering. It’s cut for someone several times heavier than me. The backseat, however, is quite nice, offering heat for the outboard passengers and miles of legroom thanks to the crew-cab body.
Pony up, cowboy
In addition to that AT4 Premium Package, this Sierra 2500 also features vibrant Cayenne Red Tintcoat paint, a $645 option, plus it’s fitted with the $545 gooseneck/fifth-wheel prep option. Including $1,595 in destination fees, it checks out for $68,160, a steep price to be certain, but one that’s not totally unreasonable for the capability it offers. That figure is also in line with a comparably equipped Ram Power Wagon or a Ford F-250 with the Tremor package.
The 2021 GMC Sierra 2500 is capable and hard-working. It’s a truck I can respect, even if it’s one I don’t love.