The overlanding community just witnessed something extraordinary at Overland Expo Pacific Northwest. Despite an incredibly heavy payload, the GMC bulldozed over the dips and mounds and articulated beautifully, almost like a buff, off-road-ready ballerina. This wasn’t just any truck – this was Overland Expo’s 2025 Ultimate Build, featuring the GMC Sierra 2500 HD AT4X AEV Edition paired with a fully loaded $49,945 OEV Back Country slide-in camper.
The Beast: 2025 GMC Sierra 2500 HD AT4X AEV Edition Specs
Before all the upgrades, the nearly $90,000 2025 GMC 2500 HD AT4X is no small truck. It’s a big boy truck, with a beefy 6.6-liter Duramax V8 diesel engine that has 470 ponies at the ready, but an astounding 975 lb-ft of torque. This powerhouse forms the foundation of what many consider the ultimate overlanding platform straight from the factory.
Engine and Performance Capabilities
The heart of this ultimate build is 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. With a maximum towing capacity of 18,000 pounds, this truck doesn’t just haul gear – it dominates every terrain it encounters.
The Duramax engine brings significant advantages for long-range overlanding:
- Impressive fuel economy for a heavy-duty truck (14-17 mpg combined)
- Extended service intervals reducing maintenance stops
- Integrated exhaust brake for superior control on steep descents
- Exceptional torque delivery for climbing and maintaining efficiency over long distances
Advanced Off-Road Technology
What sets the AT4X apart is its sophisticated suspension system. 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.
These aren’t ordinary shocks. DSSV technology, proven in endurance racing, uses spool valves instead of traditional twin-tube or monotube designs. This provides consistent and predictable performance, especially over uneven, rocky, or rutted terrain – exactly what overlanders encounter in challenging environments.
American Expedition Vehicles (AEV) Enhancements
The transformation from capable to extraordinary happened at AEV’s facilities in Michigan. The first stop on the build journey was American Expedition Vehicles (AEV) in Wixom, Michigan, where the team installed the AT4X AEV Edition upfit that would define this truck’s ultimate capabilities.
Wheel and Tire Package
The truck was fitted with 18×9 AEV Salta XD wheels, which feature a +18mm offset to increase clearance while maintaining compliance with the fender flares. These wheels are rated for 4,100 pounds, offering the strength required for overland travel with heavy payloads.
The wheel package includes:
- 37×13.50R18 BFGoodrich All-Terrain KO2 tires
- Severe snow rating for year-round capability
- 50,000-mile warranty
- Balanced trail traction with road comfort
Protection and Recovery Systems
A ComeUp Solo 12.5rs winch was integrated into the AEV-stamped steel front bumper. Developed in collaboration with General Motors, this winch is a factory-validated component, seamlessly blending into the Sierra HD’s front-end design.
Additional protective features include:
- Heavy-duty stamped steel front and rear bumpers
- Factory-validated skid plates
- Snorkel system for improved engine performance in dusty or wet conditions
- Enhanced underbody protection for critical components
The Ultimate Overlanding Companion: OEV Back Country Camper
On the back of it was a tall, 1,345-pound $49,945 slide-in truck camper from OEV Back Country, with a stove, table, pop-up roof, seating area, and a full-sized bed. This isn’t just accommodation – it’s a complete off-grid living solution designed for four-season exploration.
Construction and Durability
The OEV Back Country represents the pinnacle of truck camper engineering. Built without wood construction, it’s designed to withstand decades of abuse while maintaining its appearance and functionality. The camper features:
- R8 insulation value on composite walls
- Fire-rated soft walls with four layers providing R4 insulation
- Powder-coated aluminum extrusions
- Gen 4 Advanced Fiberglass Composite System (AFCS) panels
Off-Grid Capabilities
| System | Specifications | Benefits |
|---|---|---|
| Water Tank | 20 gallons | Extended off-grid capability |
| Water Heating | Truma AquaGo hybrid system | On-demand hot water 24/7 |
| Refrigeration | Full-size unit | Fresh food storage |
| Sleeping | Four-person capacity | Family-friendly adventures |
| Heating | Truma VarioHeat comfort furnace | Four-season comfort |
| Electrical | Inverter system | Power for devices and appliances |
| Weather Protection | Retractable awning | Outdoor living space |
Conquering the Overland Expo PNW Off-Road Course
The real test came at Overland Expo Pacific Northwest, where this ultimate build faced a specially designed off-road course that challenged every aspect of its capabilities.
Articulation and Handling
Then came the articulation section, which is where I realized the truck was much more nimble than I originally assumed. Despite an incredibly heavy payload, the GMC bulldozed over the dips and mounds and articulated beautifully, almost like a buff, off-road-ready ballerina.
The combination of advanced suspension technology and careful weight distribution allowed this massive rig to navigate obstacles that would challenge much smaller vehicles. The DSSV dampers proved their worth, providing consistent control and comfort even with the substantial camper load.
Steep Terrain Performance
One of the most challenging sections involved steep off-camber climbs designed to test wheel placement and vehicle stability. After I waltzed through that, I drove up to a steep off-camber climb. The course crested abruptly with the terrain dropping off on either side, designed to teach the driver about wheel placement.
The longer wheelbase and added width required different driving techniques compared to smaller off-road vehicles, but the truck’s stability and power delivery made these adjustments manageable even for drivers new to such a large platform.
Technology Integration and Safety
Modern technology played a crucial role in the truck’s performance. The electronic locking rear differential provided essential traction when needed, while the integrated systems maintained vehicle stability throughout challenging maneuvers.
Educational Value: Overland Expo’s Training Program
The course is a $75 add-on to the event’s admission ticket, and it’s a two-day course. The first day is a full-day class, where certified and experienced 4×4 instructors go over the basics like how to use a winch safely, when to use a winch, the differences in transfer case speeds, when to use them, and so much more.
This educational component demonstrates how proper training can maximize the capabilities of even the most advanced vehicles. Understanding the technology and techniques allows drivers to safely push the boundaries of what’s possible in challenging terrain.
The Ultimate Build Program’s Impact
Now in its fifth year, the Ultimate Build program allows Overland Expo’s editorial team and overland gurus to transform proven factory vehicles into their interpretation of the Ultimate Overland Build. This program serves multiple purposes:
- Showcasing the potential of factory platforms
- Demonstrating real-world applications of aftermarket components
- Providing inspiration for the overlanding community
- Supporting the Overland Expo Foundation through eventual auction
Community and Conservation
The Ultimate Build, which is a sponsored build designed to draw excitement at the Expo’s events and various retailers, will be auctioned off after this year’s Expo events. All proceeds will go back to the Expo, so the organizer can continue growing the events to bring more overlanders—experienced and otherwise—to learn and explore.
Future of Overlanding: What This Build Represents
The 2025 GMC Sierra Ultimate Build represents more than just an impressive off-road vehicle – it’s a vision of how overlanding can evolve. By combining factory engineering with thoughtful aftermarket enhancements, this build demonstrates that serious overlanding capability doesn’t require starting from scratch.
The success of this ultimate build on Overland Expo’s challenging course proves that with proper preparation, training, and equipment, adventurers can confidently tackle remote destinations while maintaining the comfort and convenience of home. This represents the future of overlanding: sophisticated, capable, and accessible to a broader range of outdoor enthusiasts.
Whether you’re planning weekend camping trips or months-long expeditions, the lessons learned from this ultimate build provide a roadmap for creating your own adventure-ready platform. The combination of proven factory engineering, targeted upgrades, and comprehensive off-grid living solutions sets a new standard for what’s possible in the overlanding world.