2026 GMC Sierra 2500HD/3500HD AT4: Marion Buyers Guide

Standard equipment that's actually off-road hardware

AT4's case is straightforward: the Off-Road Suspension Package, with twin-tube Rancho shocks and underbody skid plates, ships standard rather than as an add-on. Combined with the exclusive 20" gloss-black wheels and available BFGoodrich off-road tires, AT4 is built to be trail-capable off the lot, not after a trip to the parts counter. Adaptive Cruise Control with trailering is standard here too — a genuine step up from Pro through SLT, where it's only available.

Real terrain around McDowell County

Curtis Creek and the Pisgah District's forest roads sit a short drive from the dealership, and the Blue Ridge Parkway climbs past Marion's back door — genuine terrain for a truck built with a factory off-road suspension package and up to 14 available camera views, not just marketing language. The exclusive Jet Black interior with Kalahari accents pairs standard heated and ventilated perforated leather front seats with the trim's off-road identity, so a day on the forest roads doesn't have to mean giving up comfort on the drive up.

Diesel is available, not standard, on AT4

Worth flagging directly: unlike some other GMC trucks where AT4 pairs automatically with the diesel engine, Sierra HD's AT4 ships with the same standard 6.6L V8 gas engine as every trim below Denali Ultimate. The Duramax 6.6L Turbo-Diesel is available as an upgrade on AT4, same as on Pro, SLE, and SLT — it's not bundled in by default, so a diesel-focused AT4 buyer needs to specify it when building and pricing the truck.

What the reviews say about buying an off-road-capable truck

Buyers who travel distance for a specific truck show up regularly in [Jim Cook GMC]'s review history — a pattern that matters for a trim like AT4, which draws serious truck shoppers willing to look beyond their immediate area. One out-of-state buyer described the process: "Just purchased a great truck from this dealership and couldn't have had a better experience, especially considering I was purchasing from out of state. Evan (salesman) and the entire team were very professional, helpful, honest and quick to respond throughout the process. He was even willing to meet me halfway with the truck the very same day of the purchase" — Evan Johnston, a Sales Consultant on staff.

Frequently asked questions

Is the off-road suspension standard on AT4, or an add-on?

Standard — the twin-tube Rancho shocks and skid plates ship on every AT4, not as a package or dealer add-on.

Does AT4 come with the Duramax diesel by default?

No. AT4's standard engine is the 6.6L V8 gas, same as Pro through SLT. The Duramax is available as an upgrade, the same as on every trim except Denali Ultimate.

What's the difference between AT4 and AT4X?

AT4 gets a genuine off-road suspension package and standard adaptive cruise with trailering. AT4X goes further with a factory 1.5" lift, front-and-rear-capable dampers from Multimatic, a rear electronic-locking differential, and 35" tires — more hardware, a higher price, and (per GMC's current spec pages) offered on the 2500HD specifically.

Is AT4 available with all-terrain or off-road-specific tires?

Yes — AT4's exclusive 20" gloss-black wheels are available with BFGoodrich off-road tires, on top of the standard suspension hardware.

The bottom line

AT4 is Sierra HD's answer for a buyer who actually wants to use forest roads, tow through mountain weather, or just wants genuine off-road confidence as standard equipment rather than an upsell. For McDowell County terrain specifically, the standard suspension package and available off-road tires earn their price step over SLT without requiring the bigger jump to AT4X.