It was just a matter of time before the 2024 GMC Sierra HD AT4X followed on the heels of the Chevrolet Silverado HD ZR2, unveiled earlier this month. Chevy, Ford and Ram have been at each other’s throats with off-road specific pickups across all segments, including heavy duty trucks, which were once content with being known for their high towing capacities. Now that American automakers are heavily invested in the off-road, heavy duty trucks have been dragged into the mud, and that means the Sierra HD is getting an AT4x badge.
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While the previous Sierra HD was available in the off-road ready AT4 trim, this all-new model will append an “X” to that, thereby rounding out the lineup of AT4X trucks available from GMC: from the mid-size Canyon AT4X, to the full-size Sierra AT4X, and, now, the fullest of sizes with the Sierra 2500 HD AT4X.
There will also be a Sierra HD AT4X AEV Edition, which builds upon the base model with all the farkles off-roaders yearn for, straight out of the gate. Things like stamped steel bumpers with integrated recovery points and a front winch, steel skid plates to keep the steering gear and transfer case safe, and unique 18-inch wheels bearing the AEV logo wrapped in 35-inch Goodyear mud-terrains.
I guess the Sierra HD’s famous Duramax and Allison badging alone are not the draw they once were — at least, not in a world of F-Series Super Duty Tremors and Ram 2500 Power Wagons. And while the Chevy Silverado HD ZR2 could have covered whatever use-cases such trucks serve the GM faithful, it makes little sense to not release a GMC model, which offers buyers luxury on par with the off-road and towing tech found on this “professional grade” Sierra HD.
Like the Silverado HD ZR2, the Sierra HD AT4X will feature Multimatic DSSV dampers — characteristic of the ZR2 and AT4X lines — as well as beefy upper and lower control arms, steering knuckles, and e-locking differential at the rear. But it wouldn’t be a heavy duty truck without a diesel, so the first-ever Sierra HD AT4X will be available with a Duramax 6.6-liter V8 turbodiesel engine. The V8 turbodiesel will make 470 horsepower and 975 lb-ft of torque, with max torque coming on at 1,600 rpm. The standard gas engine is similar in size: it’ll be a 6.6-liter V8 that makes 401 hp and 464 lb-ft of torque.
Both engines will be paired to an Allison 10-speed automatic transmission, and both powertrains will have the same fuel capacity of 36 gallons. GMC has not released any details regarding fuel efficiency for the HD AT4X, but something tells me the target audience for these trucks will be mildly concerned, at best, about the Sierra HD’s mpg numbers. Towing isn’t exactly a fuel-sipping enterprise to begin with and neither is off-roading, for that matter.
While the Sierra HD AT4X is not for the faint of heart at the fuel pump, the truck will tow 16,000 pounds if drivers opt for the V8 gasser, and up to 18,500 pounds if drivers go for the V8 turbodiesel. Of course, there’s a weight penalty to deal with as the diesel-powered Sierra HD AT4X weighs in at 8,237 pounds, versus the gas-powered model at 7,516 pounds. And the diesel Sierra HD AT4X AEV Edition is the heaviest of the bunch, weighing in at 8,605 pounds.
Whether that’s too heavy to be useful on even a slightly technical trail, I leave up to you. For what it’s worth, GMC says the ground clearance of the Sierra HD AT4X is 11.6 inches, while the approach, departure and breakover angles are 31.6, 25.7, and 21.2 degrees, respectively.
The newest, gnarliest Sierra HD also adds an off-road mode (on top of its eminently useful towing mode) that enables the truck to dial in the throttle map, traction and stability control to make off-roading this behemoth easier. I’d still feel a lot more comfortable in a Canyon AT4X (review forthcoming) when the trail gets tough, but this hauler is for drivers who want to tow much more than any mid-sizer, while still having some off-road capability. GMC says the 2024 Sierra HD AT4X and AT4X AEV Edition will be at dealers later this year, in the fall. And we’ll know what they’ll cost as their release date draws near.
