By Matt Feldermann
For overland travelers who push the boundaries of adventure, choosing the right vehicle is essential. It must be tough, capable, and reliable, yet comfortable enough for extended living. Enter the 2025 GMC Sierra 2500 HD AT4X AEV Edition — a heavy-duty truck purpose-built for off-road travel, long-distance expeditions, and overlanding setups like this year’s Ultimate Overland Vehicle. Now in its fifth year, the Ultimate Build program gives Overland Expo’s editors a chance to take a venerable factory vehicle foundation and turn into their vision of the Ultimate Overland build 2025. With a factory-engineered blend of strength, off-road technology, and premium features, this truck is a serious contender for the best adventure-ready platform available straight off the lot.
At its core, the GMC Sierra HD AT4X is a heavy-duty workhorse, featuring a fully-boxed high-strength steel frame designed to handle heavy payloads and demanding conditions. The AT4X trim elevates the Sierra HD lineup’s off-road performance, thanks to additional lift height and Multimatic DSSV (Dynamic Suspensions Spool Valve) dampers — race-proven shocks that offer precise damping across all terrain types. Unlike traditional twin-tube or monotube shocks, DSSV dampers use spool valves to deliver consistent and predictable performance, especially over uneven, rocky, or rutted terrain. This technology, proven in endurance racing, now enhances overlanding rigs with exceptional trail composure.
The AT4X AEV Edition builds upon the already-capable AT4X platform by adding a full suite of trail-ready components, making the truck expedition-worthy straight from the factory. These additions include:
- Winch-capable, stamped steel AEV front bumper
- Stamped steel AEV rear bumper
- AEV fender flares
- 18” AEV wheels
- Four stamped steel skid plates protecting the radiator, IFS, transmission, and transfer case
- Exclusive AEV branding package
When the terrain gets rough, the GMC Sierra HD AT4X AEV Edition is equipped with an electronic locking rear differential, allowing the rear axle to lock completely. This delivers equal power to both wheels—a huge advantage when climbing loose grades, crawling through mud, or powering through snow.
The 2025 GMC Sierra HD AT4X AEV Edition offers two engine options:
- 6.6L V8 Gas Engine (401 hp, 464 lb-ft of torque) – A solid choice for moderate overland setups, offering great throttle response and a lower up-front cost.
- 6.6L Duramax Diesel Engine (470 hp, 975 lb-ft of torque) – The ideal choice for heavy overland builds, delivering tremendous torque for towing, climbing, and maintaining efficiency over long distances.
We opted for the 6.6L Duramax diesel engine, paired with the Allison 10-speed automatic transmission. This powertrain combination delivers smooth shifts, consistent performance under load, and proven reliability. The Duramax engine is especially well-suited for long-range travel, thanks to its impressive fuel economy (for a heavy-duty truck), long service intervals, and integrated exhaust brake for better control on steep descents.
Towing is another strength—perfect for hauling an overland trailer alongside the camper. With towing capacities exceeding 18,000 pounds and a payload rating of over 3,000 pounds, this truck allows you to bring everything you need without compromise.
While the Sierra is built for hard work, the AT4X AEV Edition’s interior prioritizes comfort, connectivity, and convenience—essential for those living out of their vehicle for extended periods. For those seeking to explore further, stay off-grid longer, and do it all in comfort and confidence, the 2025 GMC Sierra 2500 AT4X AEV Edition stands at the top of the heavy-duty overlanding world.
AEV Upfit Package
Our first stop was American Expedition Vehicles (AEV) in Wixom, Michigan, for their AT4X AEV Edition upfit package, taking this truck to the next level. The AEV upfit package builds upon the factory-installed AT4X AEV Edition content and includes:
- AEV Salta XD Wheels – 18×9 with a +18mm offset, providing extra clearance while keeping the tires under the fender flares. With a 4,100 lb. load rating, these wheels are perfect for a hard-working overland rig.
- AEV 37” Tire Clearance Kit – Allows 37” tires to fit without modifying the suspension or adding a lift.
- 37×13.50R18 BFGoodrich All-Terrain KO2 Tires – AEV’s go-to tire for heavy-duty trucks, offering outstanding traction while maintaining a smooth, quiet highway ride. These Severe Snow Rated tires come with a 50,000-mile warranty.
- ComeUp SOLO 12.5rs Winch – Designed in collaboration with GM for the Sierra HD AT4X AEV Edition’s stamped-steel front bumper. This factory-validated component integrates seamlessly.
- AEV Snorkel – Inspired by heavy-duty industrial and military applications, this snorkel delivers cleaner, cooler air to the engine — even in the worst off-road conditions.
- AEV Front Bumper Light Bar (Prototype) – AEV installed a prototype light bar on the front bumper, providing a solid mounting location for four 6” Vision X Explora off-road lights.
- AEV Paint Appearance Package– To complement the Sterling Silver Metallic exterior, AEV added their Onyx paint package to the hood, roof, and tailgate for a truly unique look.
To prepare for the installation of a slide-in camper, AEV also installed a 50-state legal Magnaflow stainless steel exhaust system for increased efficiency on long trips. Additionally, they fitted an Air Lift LoadLifter 5000 Pro Series Kit and WirelessOne air compressor, providing on-demand load support.
Home Away from Home: OEV Back Country Camper
For our Ultimate Overland Build, we opted for a slide-in camper. At the top of our list was the OEV Back Country—a rugged, pop-up truck camper designed for extreme conditions. Its removable four-season cabin, three-season water system, and R8 insulated composite walls provide durability and comfort for up to four adventurers.
Key Features:
Plumbing/Heating/Cooling
- Truma Aquago hot water
- Truma Vario cabin air heater
- 20-gallon freshwater tank, stainless steel sink and cooktop.
Electrical
- Victron 220w solar panel
- Battle Born 270Ah LiFePO4 battery
- Xantrex Freedom X 2000 inverter and control panel
- Isotherm Cruise 65 Clean Touch Stainless Steel Fridge
- Lavabox Portable Campfire
Other:
- Torklift Apex Anchors
- Dual-pane acrylic windows
- Alu-Cab 270 Awning
- Alu-Cab Shower Cube
- Opinel USA Knife Set
- Forrest Tool Co Multi-Tool (Axe & Shovel)
Bringing It All Together
For the final stage of the build, we turned to Tiny Rig Co. in Southern California. With expertise in high-end overland builds and impeccable attention to detail, they completed the project flawlessly.
Tiny Rig Co. wired up our nine forward-facing Vision X Explora lights, along with two Vision X Optimus 3” auxiliary lights in the rear bumper. They also installed a Switch Pros SP9000 system to manage the lighting, plus a Midland MXT575 CB radio for trail communication between vehicles.
A home for everything
The interior of the GMC Sierra HD AT4X AEV Edition is for a lack of better words, stunning. We did not want to change anything, so we focused on accessories that offered additional storage for gear and accessory mounting locations. The Tackform TRAXX system was the perfect dash-mounted solution for holding our phone and tablet when using OnX offroad maps. Keeping track of all the small items in the truck is super easy with the addition of our ONWRD Supply Co. seat back organizers, which are available in a nearly endless number of configurations.
Airing-up after a day on the trail is fast and easy, with our high-efficiency Viair Portable Air Compressor on-board. Should we find ourselves with a flat tire, Rig Ready Systems provided us with their new Jackout HD kit. This kit includes everything to assist you with changing your flat — a Rigid impact gun, extra battery, emergency flares, multitool, emergency IFAK, jack, and more! Best of all, it packs away neatly in a robust storage case. This is organization at its best.
Never out of reach
Finally, keeping in-touch with the outside world has never been easier thanks to our Redzone Wireless internet. We have relied on this system for sending emails, streaming music and even watching sports on TV. In the event of an emergency, we also have a Zoleo Satellite Communicator, which extends smartphone messaging coverage to virtually anywhere on the earth.
Final Thoughts
The GMC Sierra HD AT4X AEV Edition + OEV Back Country Camper has exceeded our expectations in every way. With cutting-edge technology, premium amenities, and unmatched capability, this truly is the Ultimate Overland Adventure Vehicle.
About Ultimate Build
As part of the 2025 Ultimate Overland Build, the GMC Sierra HD AT4X travels to all Overland Expo events: Overland Expo West, May 16-18 in Flagstaff; Overland Expo Pacific Northwest, June 27-29, Redmond, Oregon; Overland Expo Mountain West, August 22-24, Loveland, Colorado; and Overland Expo East, October 3-5 in Arrington, Virginia.
At the end of the schedule, the vehicle and all of its overlanding components are auctioned off on Bring A Trailer to raise funds for the Overland Expo Foundation, supporting grants to organizations and individuals that support overlanding, protecting access to or improving public lands, providing education that fosters preparedness and a more conscientious community, and promoting responsible exploration for the overlanding community.
For more information, visit overlandexpo.com/ultimate-overland-vehicle and follow @overlandexpo on Instagram, YouTube, and Facebook. You can track content with #ultimatebuild2025.
About Overland Expo
Founded in 2009, Overland Expo is the world’s premier event series for do-it-yourself adventure travel enthusiasts. Hundreds of vendors of adventure travel equipment, camping gear, bikes, vehicles, and services convene at every Overland Expo event. Each Expo hosts hundreds of session-hours of classes, including for off-road driving techniques, adventure motorcycling, inspirational programs, roundtable discussions, demonstrations, as well as the Overland Film Festival. Overland Expo is owned and produced by Emerald.
About Emerald
Emerald’s talented and experienced team grows our customers’ businesses 365 days a year through connections, content, and commerce. We expand connections that drive new business opportunities, product discovery, and relationships with over 140 annual events, matchmaking, and lead-gen services. We create content to ensure that our customers are on the cutting edge of their industries and are continually developing their skills. And we power commerce through efficient year-round buying and selling. We do all this by seamlessly integrating in-person and digital platforms and channels. Emerald is immersed in the industries we serve and committed to supporting the communities in which we operate. As true partners, we create experiences that inspire, amaze, and deliver breakthrough results. For more information, please visit emeraldx.com
