2024 GMC Sierra HD AT4X & AT4X Extreme AEV First Look: Big Trucks For Luxe Off-Roading

Near the end of April, I rolled into North Carolina to experience the new 2023 GMC Canyon AT4X and the 2024 Chevrolet Trax. None of those invited for that experience — including yours truly — knew GMC had a big surprise waiting for us at "Camp Canyon" (a.k.a. Asheville River Cabins in Arden, North Carolina) the night before the Canyon outing, though. And I do mean big. Joining the GMC AT4/AT4X hardcore off-road family in the 2024 model year is the Sierra HD AT4X, which includes the Sierra HD AT4X AEV Edition outfitted by American Expedition Vehicles. Both machines arrived near the central gathering spot at the camp, one draped in a lovely shade of Volcanic Red, the other in a stunning silver pulling a trailer with yet another mystery onboard.

Debuting for the 2019 model year with the Sierra 1500, the AT4 line provides plenty of off-road capability to GMC's "Professional Grade" machines, including four-wheel drive standard, hill descent control, factory off-road suspension, skid plate, and grippy all-terrain tires. As of the 2023 model year, the Acadia, Canyon, Sierra, Sierra HD, Terrain and Yukon can all be had with the combination of off-road enhancements and premium features the AT4 is known for. The "X" in AT4X takes things up to 11 for the ultimate GMC off-roader, with a little help from Canadian engineering company Multimatic, known for building majestic machinery like the third-gen Ford GT (and the race-ready Ford GTE), the Porsche 963, and the upcoming GT4 and GT3 variants of the seventh-gen Ford Mustang. Those road-and-track engineering skills come quite handy for the trail, too.

The heaviest AT4 gains more off-road knowledge

"GMC's AT4X trim, which will be available across the entire GMC truck lineup, offers customers more premium choices when it comes to 'do-it-all' capabilities," said Duncan Aldred, Global Vice President of Buick-GMC, in a statement. "Each model delivers unique strengths, with the all-new Sierra HD AT4X taking it to the max, giving our customers the most luxurious and most off-road capable HD we've ever offered. AT4X means you can conquer almost any terrain, in complete comfort and with the towing power to bring your recreational toys, gear or camper along for the adventure."

So, what does the "X" in AT4X get you, especially in a truck whose original intent is to pull big boats to the marina and hot-shot odd loads across the country? For one, a max trailering capacity of up to 18,500 pounds, so long as you check the 6.6-liter Duramax turbo-diesel V8 on the options list; a 6.6-liter gasoline V8 is standard. That optional diesel hit the gym for the 2024 model year, bulking up to 470 horses and 975 lb.-ft. of torque. 

All that power, which goes through a standard Allison 10-speed auto, will have plenty of room to spread out across the desert plains as far as the power band goes. And they'll reach whatever terrain awaits through a full set of 35-inch Goodyear Territory all-terrains, while the truck itself rides high with a factory-installed 1.5-inch lift kit enhanced with Multimatic's DSSV (Dynamic Suspension Spool Valve) dampers, which have been used in everything from the GMC AT4X line to the Chevrolet Camaro ZL1 1LE and Ferrari SF90 Stradale Assetto Fiorano.

AEV takes the X in AT4X to the extreme

There's more, of course, with the 2024 GMC Sierra HD AT4X. The off-road enhancements for the heaviest Sierra include a rear locking e-differential, ultra beefy front upper and lower control arms and steering knuckles, and big steel and aluminum skid plates to protect the powertrain from whatever rocks protrude from the trail. Not to mention the all-new Off-Road Mode, which adjusts the Sierra HD AT4X's various systems for the best performance far, far away from the pavement. The new system also manages throttle progression and transmission shifting for every situation along the beaten and rutted path.

If you need even more off-road capability, though, then you'll need to step up to the 2024 GMC Sierra HD AT4X AEV Extreme Edition. Outfitted by American Expedition Vehicles of Wixom, Michigan, the AEV Extreme Edition brings the "HD" with a pair of stamped steel bumpers with integrated recovery points and an integrated winch up front. The powertrain, transfer case and steering gear receive a full set of heavy-duty steel skid plates for protection, and those Goodyears mentioned earlier are wrapped around a set of inky black 18-inch Salta wheels.

"The Sierra HD is an ideal foundation when it comes to on-road performance, off-road capability and insane pulling power," said AEV CEO and founder Dave Harriton in a statement. "As with the Sierra 1500 before it, we took AEV's signature performance-driven approach and dedication to detail to elevate the aspects that off-road customers want and demand in their heavy-duty truck. The result is an awesome truck with capability and confidence in all the right spots."

The X is for Xtreme comfort, too

When it comes to factory off-roaders, there are two ways to go about handling the interior. One way, as demonstrated by the Ford Bronco Everglades, is focusing more on the necessities, from marine-grade vinyl seating to rubberized floors with built-in drainages for easy cleaning after a day in the deepest of mud puddles.

Then, there's GMC's way. Already the luxurious sibling to Chevrolet's more down-to-earth Silverado HD, the 2024 Sierra HD in AT4X trim continues with this line of thinking to make even the roughest of rough country more like flying over it in a G6. The exclusive Obsidian Rush interior with Vanta Ash wood trim welcomes everyone to a comfortable journey over the hills and through the woods to Grandma's house. Every seat in the cab is blanketed in full-grain leather, while the front occupants receive power massaging while the Sierra HD AT4X power-massages its way through the Rubicon Trail and Moab.

Step up to the Sierra HD AT4X AEV Extreme Edition, and you'll find the headrests branded with AEV's logo stitched into the leather, just above the AT4X logo at top of the seatback itself; AEV badging can also be found on the exterior, just in case everyone wants to know what your Sierra HD AT4X is all about. White and red stitching with piping trims out the seats, with more red stitching finding itself on the armrests of the doors. All in all, no one will go without a comfy place to experience the rugged outdoors.

Technology makes the rugged outdoors fun and safe

Of course, you can't have a factory off-roading rig these days without technology making room for itself on the trail. The 2024 GMC Sierra HD AT4X and Sierra HD AT4X AEV Extreme Edition bring all the bells and whistles to the next overlanding adventure, starting with a 12-speaker Bose Premium Series system with Centerpoint surround-sound for enjoying all of your favorite classic country songs on SiriusXM. And speaking of, you'll be able to access satellite radio and more through the all-new 13.4-inch infotainment touchscreen in the center console, just above the HVAC unit with (very much welcomed) big chrome knobs. Throw in a 12.3-inch gauge cluster and a 15-inch heads-up display, and you and yours will have plenty of info to work with, no matter where you are.

The tech party doesn't stop with the usual suspects, though. The Sierra HD AT4X and Sierra HD AT4X AEV Extreme Edition have you covered when it comes to pulling everything from a rugged camper/full-service mobile off-road repair shop to a Class 8 off-road race truck competing in the Mint 400, thanks to a whole suite of trailering tech dubbed the ProGrade Trailering System. There's the industry-first Transparent Trailer view for gooseneck and fifth-wheel trailers, blind-spot alert, adaptive cruise control with trailer, and up to 14 camera views.

A welcome addition to the AT4X family

It means GMC is pretty confident it has an AT4/AT4X for nearly everyone in nearly every situation — aside from the returning compact truck market, though the automaker says "stay tuned" for that one. The 2024 Sierra HD AT4X and Sierra HD AT4X AEV Extreme Edition are both welcome additions to the growing family of the most "Professional Grade" of off-roaders. Those interested in bringing home the heaviest members of the family will need to be patient until the third quarter of 2023 before the new trucks arrive on dealer lots. Pricing for the big boys will be announced closer to release, though if the 2024 Sierra HD AT4 is any indication — with its starting MSRP of $69,100 — you'll be paying quite a bit.

Meanwhile, we can't forget what the silver Sierra HD AT4X AEV Extreme Edition pulled into Camp Canyon. The mystery truck above, per the GMC engineers at the camp, is a Canyon, but that's all they could be coaxed into telling me. Perhaps it, too, is an AT4X outfitted by AEV? Guess we'll have to return to Camp Canyon one day to be properly introduced.