The 2024 GMC Sierra HD AT4X AEV Climbs, and Moves, Mountains

The GMC Sierra HD AT4X AEV is as long as a line of 20 people. It's strong enough to relocate up to 18,500 pounds of earth or pull the enormity of a single EarthRoamer. It's the heaviest Sierra HD sold, with a crushing 8605-pound claimed curb weight. With its mirrors extended, it's wider than a full-size school bus, and if you thought the regular Sierra HD was tall, the AEV version reaches nearly two inches further into the sky. While its dimensions illustrate how cartoonishly huge the biggest pickups have become, the AT4X AEV also gives GMC's mightiest pickup truck serious capability.

Taking the already off-road-equipped Sierra HD AT4X to the next level, the AT4X AEV gets the American Expedition Vehicle treatment. That includes AEV stitched headrests and as many badges as the local police precinct, but there's also useful stuff, such as the hot-stamped steel front and rear bumpers.

The Sierra HD AT4X AEV comes exclusively as a 2500HD crew cab with the standard 6-foot 9-inch bed and four-wheel drive. Both the 401-hp 6.6-liter V-8 gasser with 464 pound-feet of torque and the preferred 470-hp turbocharged 6.6-liter V-8 Duramax diesel powerplant with an epic 975 pound-feet of torque are offered. A 10-speed automatic transmission bolts to either, but the final drive ratio for the gas engines is 3.73:1 while diesels get 3.42 gearing. Both powertrains slurp from a 36-gallon fuel tank.

The 35-inch Goodyear Wrangler Territory MTs wrapping AEV's exclusive 18-inch aluminum wheels add to this package's rugged premise. Don't let the big-truck guys in on a little secret: The mid-size Canyon AT4X AEV is on the same tires, just mounted on smaller 17-inch wheels instead.Our time with the AT4X AEV was completely off-road, so we can't report on their highway-speed noise level.

The AEV has the same 1.5-inch suspension lift as the HD AT4X and includes its Multimatic DSSV dampers, which are unlike anything from other off-road-themed heavy-duty pickups from Ram and Ford. The spool-valve dampers create a shockingly smooth ride as they soak up the ohs and ouches of uneven off-road terrain.