GMC’s marketing people like to draw comparisons between the new 2020 Sierra 2500 AT4, the new heavy-duty off-road trim, and Ram’s venerable 2500 Power Wagon. But that isn’t really a fair comparison, because these two trucks are very different in how they approach their off-roading duties. The Ram’s primary function is to be the ultimate off-road HD pickup, featuring manually lockable front and rear axles, electronic sway-bar disconnects, a super-low crawl ratio, a 12,000-pound winch neatly integrated into the front bumper and more gear meant to help it go over the most treacherous terrain. The GMC Sierra 2500 AT4 doesn’t have any of that kit. What it does have that the Power Wagon doesn’t is an optional 6.6-liter Duramax diesel engine, the ability to tow a hefty 18,500 pounds, and twice the payload capacity. It sounds more like a competitor for Ford’s upcoming Super Duty Tremor Off-Road Package, a lifted, off-road-oriented trim that also still focuses on people who want to tow.
We drove the new 2020 Sierra 2500 AT4 at a media launch event in Jackson Hole, Wyo., where we were able to put the new truck through some of its paces on and off the pavement. (Per our ethics policy, PickupTrucks.com pays for its own lodging and airfare at such automaker-sponsored events.) And while the 2500 AT4 is no off-road mountain goat like the Power Wagon, its ability to tow and haul with ease puts it in a different light than that truck.
What You Get With the HD AT4
The first and most obvious visual difference between the AT4 and the fancier GMC Sierra 2500 Denali is the intentional lack of brightwork on the truck. Most of the chrome has been banished in favor of body-color or blackened trim pieces, and the resulting look is modern, intimidating and distinctive, especially in darker colors like red or black. The AT4 brings some capability as well. It has Rancho shock absorbers, additional skid plates and an Eaton automatic locking rear differential; the same bits as the X31 off-road package available on non-AT4’s. You also get the Sierra HD’s new automatic four-wheel drive, which can be selectively locked or left in automatic, and which features a low range as well. It rides on 18-inch Michelin all-terrain tires with 20-inch models as an option. What the truck does not feature are selectable locking differentials, giving an advantage to the Ram Power Wagon in certain off-road situations.
Where the AT4 has a distinct advantage over the Power Wagon is in the powertrain department. While the Power Wagon’s stout 6.4-liter gasoline Hemi V-8 engine and eight-speed transmission is a dynamite combo, with plenty of power for just about any situation, it’s outgunned by the latest GMC 6.6-liter gasoline V-8, which produces slightly less horsepower (401 versus the Ram’s 410) but a lot more torque (464 pounds-feet versus the Ram’s 429). You only get a six-speed automatic with the GMC gas engine; the Power Wagon upgraded to an eight-speed for 2020. But if you’re looking for the ultimate in torque, you’ll want to go the GMC route and opt for the revised turbo-diesel 6.6-liter Duramax V-8 engine mated up to an all-new 10-speed Allison heavy-duty transmission. The diesel puts out 445 hp and a whopping 910 pounds-feet of torque, more than twice what you can get in a Power Wagon, which does not offer a diesel engine. We don’t know how this will compare with the new 2020 Ford Super Duty’s latest Power Stroke V-8 engine, as Ford continues to avoid sharing any power or torque numbers for its latest truck.
I’ve sampled the new 6.6-liter gasoline V-8 in the Chevrolet Silverado 2500, and found it to be an outstanding motor. The turbo-diesel 6.6-liter Duramax is equally fantastic, but it might actually be overkill in your Sierra 2500 AT4 unless you plan on regularly towing with it, which, according to GMC’s customer research, you probably do. My first drive consisted of a new 2500 AT4 crew cab with 2,000 pounds of logs strapped in the bed. While that kind of weight over the rear does affect the handling a bit, there didn’t seem to be much squat to the back, and overall steering remained steady and true, not light and flighty. Of course, 2,000 pounds is still well short of the Sierra 2500 crew cab’s maximum payload rating of 3,597 pounds when equipped with a diesel engine (3,862 when you go with gas), but this is also not the AT4 trim’s maximum either given the added weight of its off-road components (which would be 3,615 pounds, per GMC).
Off-Road Truck, but Not Very Far Off-Road
I briefly took the AT4 off-road, but the course wasn’t anything challenging, just two-tracking through a couple of fields. Still, on those disheveled surfaces, the AT4’s suspension nicely damped the rough terrain and maintained a level of comfort and control in the cabin that worked well. It feels more civilized than a Power Wagon, cushier and less rugged, but this was also a function of having significant payload in the back. I’ve done things in a Power Wagon that I wouldn’t consider doing in an AT4, given the lack of manual control for the differentials and sway bars. So for lighter-duty off-roading, the AT4 seems well suited.
But towing is where GMC believes the AT4 shines, and that’s a correct assumption. My run consisted of towing a 12,000-pound box trailer over 55 miles of Wyoming high country, and the big 2500 didn’t skip a beat. You’ll notice the weight in the longer stopping distances, but it never felt as if the trailer was pushing the truck around or that it was burdened unduly by its presence. Acceleration, even up 4-5 percent grades, was present and impressive, and the AT4’s taller, softer off-road suspension didn’t seem perturbed at all by the trailer. The truck felt level, balanced, and at ease towing such a load. The maximum a single-rear-wheel Sierra 2500 crew cab can tow from its bumper is 18,500 pounds with the diesel or 14,500 pounds with the gas engine. With a gooseneck/fifth-wheel hitch, the 2500 can tow 18,500 pounds with the diesel or 16,700 pounds with the gas engine. If you upgrade to the 3500 AT4 single-rear-wheel crew cab, you can tow 20,000 pounds off the bumper with the diesel or 14,500 pounds with the gas engine. Goosenecks and fifth-wheels improve those numbers for the 3500, allowing the AT4 to do 16,500 pounds for the gas engine, and reaching 21,300 pounds for the diesel. To really maximize your towing ability, you need a dual-rear-wheel diesel regular-cab model, which will bring you that 35,500-pound max tow rating — but the AT4 isn’t available in a dual-rear-wheel configuration, nor would you really want a setup like that for going off-road.
Where the Sierra HD AT4 truly shines is in that sweet spot for customers who want a decently off-road capable truck, but still see the primary function of the vehicle as a towing rig. It serves that role admirably, augmented mightily by its class-exclusive ProGrade Trailering towing camera system, which with the addition of accessory cameras can bring 15 different camera views into the cabin to help a driver see all around the vehicle when towing. It even stitches camera views together to make the trailer seem invisible. The AT4 the Power Wagon’s more straightforward off-road focus, and will likely continue to be the choice in this class until we get our hands on the new 2020 Ford Super Duty F-250 Tremor to see how it compares.
I’m almost tired of reiterating the same complaints about the latest GM trucks in every review, but they consistently have been the same issues. As good as the trucks are with regard to capability, they fall short of the competition on interior quality and sophistication. The AT4 gets some unique Kalahari brown accents in its otherwise dour monochromatic black cabin, but it still can’t hold a candle to a Ram interior. It’s not just the choice of materials, either, it’s the execution of the fit and finish that started in the design stages. Why is all the fake wood trim below my knees? Why is the interior door latch handle a two-piece affair with a sharp seam? Why does a truck this expensive have so much flashing on its plastic molded pieces? There are rumors of a crash redesign for the GM trucks interiors, and one hopes it’s true, as it’s the biggest thing holding these trucks back from being smash hits.
The interior functions well enough, however, with big seats that are comfortable and an almost obscene amount of room for passengers in the second row of the crew cab. It’s also quiet in the cabin, with wind and engine noise nicely muted, if not exactly eliminated. Visibility out of the cabin is good in all directions except up, thanks to a windshield that feels short and bunkerlike, but the low beltline helps drivers see to the sides and rear. There’s plenty of storage space inside as well, with a center console that isn’t quite as versatile as a Ram’s for holding personal electronics, but it does offer plenty of space for storing bulky items.
The multimedia system works well, but it’s starting to seem like it’s behind in the display department. Ram’s big 12-inch vertical screen is making everyone else’s seem small, but even the smaller 8.4-inch Uconnect touchscreen Ram offers is bigger than the 8-inch screen in the Sierra. Apple CarPlay and Android Auto are standard and easily accessed. What the Sierra does offer that the others don’t is a full-color, super-wide, head-up display that’s standard on the AT4, and it really does look dynamite but disappears when you put on polarized sunglasses. The GMC offers some other nifty technology as well, such as the aforementioned ProGrade Trailering camera system that’s invaluable if you plan on towing, and the new MultiPro tailgate that is less valuable when you’re towing as opening it to its full extension means it’s going to smack the hitch ball if you’ve left one in the bumper’s trailer hitch. Aside from that design quirk, the MultiPro tailgate is a slick feature that actually does prove useful, making the tailgate function as any number of things from a table to a bench, folding up for easy access to the bed or acting as a traditional tailgate.
The new Sierra 2500 HD AT4 is available only in crew-cab configuration, but it can be had with a standard or long bed. The standard bed starts at $59,295 (all prices include destination), while the long bed is just $200 more. The 6.6-liter gas engine is standard, and upgrading to the 6.6-liter turbo-diesel and Allison 10-speed automatic transmission will run you $9,890. Four-wheel drive is standard on the AT4 model. My test truck had the AT4 Premium Package, which adds a sliding power rear window, the premium infotainment system with navigation, Bose premium audio system, LED roof marker lamps, lane change alert with blind spot detection and rear cross-traffic alert, 20-inch wheels and black side steps for $4,215. Another $2,125 brought the Technology Package with its HD surround-view cameras, rear camera mirror, head-up display and 8-inch digital gauge cluster information center. Add in a power moonroof, Driver Alert and Gooseneck/5th Wheel packages, and more, and the grand total came to $77,010. Of course, you can also get less expensive 2020 GMC Sierra 2500 models, as GMC announced pricing for the entire lineup earlier this year. The base price for the least expensive model, a 2500 regular-cab long bed, is $37,195, with the pricing stretching up to a 3500 crew-cab dually Denali for $67,895. Total as-tested prices are expected to top the mid-$80,000 range or potentially hit $90,000 if you check every single one of the boxes.
From a pricing standpoint, that actually puts it about on par with the Power Wagon, which generally comes in about $10,000 less, but then doesn’t offer that $10,000 diesel engine option. You can order other Ram HD models with an Off-Road Package, and it includes a decent amount of equipment like Bilstein shocks, skid plates, and tow hooks. Chevrolet doesn’t offer an equivalent trim level for the Silverado 2500 models; the TrailBoss trim is limited to the Silverado 1500 light-duty trucks. How the new AT4 stacks up to the upcoming Ford Super F-250 Duty Tremor remains to be seen, as pricing information is a long way off for that model.
But if you’re looking for a truck with some off-road chops whose primary purpose is still to act like a dynamite towing rig, a new Sierra 2500 AT4 is worthy of consideration. It provides a combination of style, capability and unique features that make it an excellent choice.
PickupTrucks.com’s Editorial department is your source for automotive news and reviews. In line with PickupTrucks.com’s long-standing ethics policy, editors and reviewers don’t accept gifts or free trips from automakers. The Editorial department is independent of PickupTrucks.com’s advertising, sales and sponsored content departments.