2026 GMC Sierra 2500HD/3500HD AT4X: Marion Buyers Guide

The suspension is the headline, and it's real hardware

AT4X's factory 1.5" lift rides on Multimatic DSSV dampers — the same damper technology used in motorsport applications, tuned here for a heavy-duty truck rather than a track car. Paired with the rear electronic-locking differential and the reinforced skid-plate package, AT4X is set up to handle terrain that would have a standard AT4 backing off. The 35" Goodyear Territory MT tires are mud-terrain rubber, standard rather than an upgrade, which is a meaningful jump from AT4's available all-terrain option.

A genuinely different interior, not just AT4 with different badges

AT4X's Obsidian Rush interior — full-grain leather, technical-grain accents, and Vanta Ash wood trim — is exclusive to the trim, paired with 16-way power front seats that add massage function on top of heating and ventilation. It's a different design language from AT4's Jet Black-and-Kalahari cabin, closer in feel to a Denali than to a standard off-road truck, while keeping the mechanical hardware underneath fully off-road-oriented.

The AEV Edition, for buyers who want the factory upfit

The available AT4X AEV Edition brings genuine AEV-branded equipment: stamped-steel front and rear bumpers, stamped-steel steering-gear and transfer-case skid plates, and 18" Salta gloss-black wheels, all installed at the factory rather than through an aftermarket upfitter after delivery. For a buyer who'd otherwise shop aftermarket bumpers and skid plates separately, the factory AEV package folds that into the original purchase and warranty.

2500HD only — confirm before assuming otherwise

GMC's own spec-highlights section for AT4X, as currently published, centers on the 2500HD; a matching AT4X section for the 3500HD wasn't part of the published spec pages at last check. That doesn't necessarily rule out 3500HD availability, but it means a 3500HD AT4X buyer should confirm current build-and-price availability with Jim Cook GMC directly rather than assume it mirrors the 2500HD offering.

What the reviews say about trusting a serious truck purchase

A trim like AT4X, at the top of the off-road lineup, draws buyers who take the vetting process seriously — and that shows up in the dealership's reviews. One recent buyer, describing exactly that kind of diligence: "Truly an incredible and trustworthy team. Great prompt communication. Drove over from Knoxville. They had no problem with me getting the truck checked out by a mechanic in Asheville before purchasing. Buying process was easy. Truck was clean and in fantastic shape. I would absolutely drive 3 hours to buy from them again. Full endorsement."

Frequently asked questions

Is AT4X available on the Sierra 3500HD?

Per GMC's currently published spec pages, AT4X is offered on the 2500HD; a 3500HD AT4X section wasn't present at last check. Confirm current availability with Jim Cook GMC before assuming it applies to 3500HD.

What does the AT4X AEV Edition add over base AT4X?

AEV-branded stamped-steel front and rear bumpers, stamped-steel steering-gear and transfer-case skid plates, and 18" Salta gloss-black wheels — factory-installed, not an aftermarket upfit.

Does AT4X come with the Duramax diesel standard?

No — like AT4, AT4X's standard engine is the 6.6L V8 gas, with the Duramax available as an upgrade. Denali Ultimate is the only Sierra HD trim with the Duramax standard.

How does AT4X's suspension differ from AT4's?

AT4X adds a taller 1.5" factory lift on Multimatic DSSV dampers and a rear electronic-locking differential, versus AT4's twin-tube Rancho shocks. AT4X's tires (35" mud-terrain) are also larger and more aggressive than AT4's available all-terrain option.

The bottom line

AT4X is built for a buyer who genuinely needs, or wants, the most off-road-capable Sierra HD available — motorsport-derived dampers, a locking differential, and 35" tires standard, wrapped in an interior that doesn't feel like a compromise. It's a real step up from AT4 in both hardware and price, and worth confirming 3500HD availability directly before assuming it's offered across both chassis.