2020 GMC Sierra 2500 4WD Crew Cab AT4 Review

A Heavy Duty with its own distinct flavor

Amos Kwon, Editor-In-Chief

Positives: Burlier for more rugged adventures, best-looking of the 2500 line, huge towing power, frighteningly quick, capacious room for five, impressive storage.
Negatives: Some interior GM cheapness is obvious, not as off-road ready as the competition, seriously expensive when optioned out.
Bottom Line: The 2500 HD AT4 is a niche truck in the heavy-duty segment, but we love it for the look and the off-road capability it brings into the fold.
Most of the serious off-road prowess in the truck world is relegated to light-duty vehicles like the Ford F-150 Raptor or the Chevy Colorado ZR2. Really, only the Ram Power wagon that's based on the Ram 2500 HD and the new Ford Tremor package (for the F250 and F350) are geared toward off-road antics. Now, GMC changes all that by adding the AT4 trim to the big Sierra 2500. Not only does it look different, but it also gets significant changes to make it more rugged than the standard Sierra 2500. While it's not as hardcore as its competitors, there were quite a few upgrades made to the 2500 AT4. We drove the AT4 for a week to experience the tougher version. Read on for our full review.

Driving Experience



The AT4 uses the big V8 turbodiesel that has gob of power. It's down on torque compared to its competitors, but the new Allison 10-speed transmission's gearing is lower, making low speed smoother, as well as improving off-road manners. We rarely get the chance to exploit off-roaders, but the word on the "street" ist that the AT4 needs a bit more in terms of off-road capability to run with the competition. Areas like suspension travel and articulation, as well as tire choice, could use improvement. In terms of towing, it can't be beaten by Ram (only Ford) with up to 18,500 pounds of towing power.

Ride Quality: The AT4's off-road leaning equates to a firm ride. Over some bumps, it felt unsettled. The Ram Power Wagon is much better at on-road manners when things get less than perfect. The 2500 AT4 keeps the front independent suspension, surprisingly, but that means it could've been an even rougher ride with leaf springs.

Acceleration: The V8 is a monster, and it pulls hard with 910 lb-ft of torque, getting this heavy truck to 60 mph in a little over six seconds. That's almost frightening for something this big.

Braking: Braking was pretty smooth with no major issues. The AT4 also has exhaust braking for towing heavy loads, a must for a HD.

Steering: Steering in the AT4 has good effort but is devoid of feedback. It had no problem staying on center at highway speeds, a confidence builder when towing big loads, no doubt.

Handling: Any HD isn't exactly nimble, of course, but we had no trouble turning due to excessive body roll.




The AT4 comes with an excellent head-up display with a nifty digital inclinometer to show grade. The surround-view camera system option boosts the off-road confidence with a low-speed trail video capture, so you can see just about everything. The ProGrade Trailering package that's standard is seriously impressive and takes the hassle out of hitching and towing. It's the best system out there and makes even novices look good.

Infotainment System: The infotainment system isn't exactly mindblowing at this price, but it is easy to use. Menu icons are big and easy to read, and navigating the system is pretty easy. The presence of Apple CarPlay simplifies matters even more.

Controls: The presence of good physical controls for just about everything shy of the infotainment is very good. Knobs are large and properly knurled for grip. We'd like to see the buttons in linear fashion instead of clustered between the knobs. It's the trailering system that crushes the competition and makes the 2500 AT4 stand out.




With the changes made to the AT4 version of the 2500, the result is the best-looking version of the heavy duty truck to date. It looks rugged and sporty, at the same time. It's the interior where things could be improved, which is why it didn't achieve a higher score.

Front: There's a lot of grille here, and we wouldn't call the AT4 particularly handsome. But it fills its rugged leanings well with a lot of black trim, a simple bumper with vertical LED foglights, and some sweet red tow hooks.

Rear: We quite like the back end of the AT4 thanks to the MultiPro tailgate that adds some character, as well as the corner bed steps.

Profile: The black fender trim looks great, and the beefy front end is apparent from this view. It looks especially good in white.

Cabin: We weren't wowed by the interior. The brown seat trim looks weird (red would've been better), and there's just a bit too much GM plastic for our liking.




Although the ride is a bit unsettling, as we mentioned before, the cabin is roomy, and views are good. Like a big HD crew cab should be, the rear passengers get ample room to stretch out.

Front Seats: Seat comfort is satisfactory, but we would've liked to see wider versions like the ones found in Ram Trucks' offerings.

Rear Seats: Huge amounts of head, shoulder, and legroom make for good family accommodations.

NVH (noise/vibration/harshness): The All-Terrain tires get expectedly noisy at highway speeds, but the 2500 AT4 is otherwise pretty good at managing noise.

Visibility: The tall nose makes it hard to see in tight spaces, but the sitting position is still pretty good. Sightlines out the side windows is good thanks to large glass. Numerous camera views make the rear more than manageable.

Climate: We had no trouble with the climate system during cold weather. The standard heated/ventilated front seats are very good.




Heavy-duty trucks don't get crash tested like passenger vehicles. The 2500 AT4 does get some decent safety equipment, thankfully, but only as optional equipment.

IIHS Rating: Not tested.

NHTSA Rating: Not tested.

Standard Tech: Other than traction control, stability control, airbags, and ABS, all the safety tech standard is towing related. Oh, there is the great Teen Driver feature that limits volume and speed, and even prevents young drivers from disabling safety features.

Optional Tech: Our tester came with the rather affordable Driver Alert Package II that includes Forward Collision Alert, Lane Departure Warning, Automatic Emergency Braking, Intellibeam Headlamps, and a Follow Distance Indicator. There's also Front & Rear Parking Assist and Lane Change Alert as part of the expensive Premium Package.




There's a lot to love about the interior storage of the AT4. There's plenty of places to store large and small items, and everything is easy to reach. The bed, likewise, has ample space for just about anything you want to haul.

Storage Space: Everything is laid out well in terms of storage compartments. The wireless charging deck can accommodate the biggest of smartphones, and the center console compartments are large. Even the huge armrest has a nice top tray. Door pockets are ample, as well. The Storage Package provides partitioned storage underneath the rear seats, a tremendous convenience.

Cargo Room: The bed of the AT4 is class-leading in terms of volume. The 6'9" bed is big and easy to load.

Fuel Economy



No HD truck is good in terms of fuel consumption, but the AT4 is up there. It's heavy, has a big displacement engine, has big all-terrain tires, and rides high. Still, it did better than we thought it would.

Observed: 18.5 mpg.

Distance Driven: 127 miles.




We didn't think much of the premium Bose system found in the price $4K+ premium package, but it's decent. For a truck that costs well north of $70,000, it should have a better system.

Final Thoughts

As we mentioned before, we didn't get to exploit the AT4's towing or off-road prowess. On road, it's decent but could use less choppiness over rough pavement. In terms of overall comfort and utility, it's very good. If you want real on-road driving manners and on-road capability, we'd recommend the Ram Power Wagon over the AT4. What the AT4 does provide is great technology for towing, as well as serious towing power from a diesel engine (which the Power Wagon doesn't offer), phenomenal looks, and ample space for passengers and gear. You just have to decide if you want to spend this much.

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