It’s like a house you can take overlanding

Looking at pictures of the Overland Expo’s GMC Sierra 2500 HD AT4X Ultimate Build, it looks big, but it doesn’t look as big as it is when you’re in front of it. Before all the upgrades (which I’ll get to shortly), 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. Therefore, it’s not at all shocking to read that its max towing rating is 18,000 pounds. The Ultimate Build isn’t towing anything, but it was hauling quite a bit. 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. So, when I was invited to the Overland Expo PNW event to drive that truck on the organizer’s new off-road course exclusive to the PNW event, I was rightfully a little nervous.

Before I hopped in the borderline luxurious driver’s seat, I did the course in my Jeep to know what to anticipate from a truck with a much larger footprint. It was a blast. I was coached by Land Rover’s Sarah Batton, the first female instructor for the company’s Experience Land Rover program. I expected the truck to be a tough drive, especially with the added weight and modifications, but when I dropped it into 4Lo and hit the trail, I was shocked by how often I forgot about the camper. It was so much more stable, rigid, and capable than I could have ever imagined.

But first, let’s talk about the mods

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. The truck started in Michigan, where American Expedition Vehicles (AEV) took to improving its capabilities. The list of mods includes :

• Salta XD Wheels mated with 37” BFGoodrich All-Terrain KO2 tires
• AEV 37” tire clearance kit
• ComeUp SOLO 12.5rs winch, co-developed with GM
• AEV Snorkel
• AEV Front bumper light bar, with Vision X Explora off-road lights
• Magnaflow steel exhaust
• Air Lift LoadLifter 5000 Pro suspension kit

The insulated camper was then installed by OEV Back Country, which boasts a water heating system, a 20-gallon water tank, a refrigerator, a shower cube, an inverter, and a retractable awning. It’s the first thing I noticed when I came face-to-face with the truck. I could easily see myself living out of the back of this truck, camping in peace in the most remote places. Southern California’s Tiny Rig added a trove of customized monitoring systems to help keep an eye on all the modifications, including:

• Trackform TRAXX system
• ONWRD seat back organizers
• Viar portable compressor and Rig Ready Systems Jackout HD kit
• Redzone wireless internet and Zoleo Satellite Communicator

My first driving impression of the Ultimate Build was very, very good

From the outside, the rig is visually impressive. It’s large and in charge, and it knows it. When I hopped in to drive it, it didn’t feel or look as large as it did. Everything was easy to interpret, easy to find, and easy to activate. The shifter was a traditional column shifter instead of on the center console, which took me back to the good ol’ days. The digital gauge cluster was bright, clear, and just as simple to become acquainted with. I put the 4WD system into 4Lo by pressing a button and waited. When it locked, I shifted the truck into first and took off. Based on the maybe two minutes it took for me to orient myself, I’d say it was one of the easier trucks to decipher. 

Driving it was easy, too. The truck came with a crawl cruise control setting, where I could set it for as low as 3 mph and have the engine, brakes, and transmission do all the work while I worried about the steering, but where’s the fun in that? I remembered Sarah’s heel rolling to control the throttle, and I climbed the very first hill. The GMC’s hood was about a mile long and very tall, so all I saw for a minute was the bright blue sky.

I had to use the off-road camera system, which was another feature easily activated with a button, and I was able to see that I needed to turn a little more to the right to keep my tires on track (thanks to the tire placement prediction feature). Going down the incredibly steep hill, I was thankful the truck was lifted to improve the bumper’s approach angle. At stock height, it would have absolutely nose-dived into the soft dirt.

The course quickly picked up in intensity, though

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. 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. Ahead of me was a built 2025 Lexus LX 500h Overtrail, and watching the SUV go sideways made me very nervous for the top-heavy GMC. I immediately pictured the six-figure rig on its side, tires spinning like a turtle flipped on its back. 

But it didn’t. It climbed up the embankment without incident. I had to take the turn differently than I did in my Jeep because of the much longer wheelbase and added width, which took some getting used to, but there was little to no effort on the truck’s end. When it came to the rock crawling section, the updated suspension and larger tires ate that section of the course for breakfast. The only hiccup was that I kept forgetting about the camper because the truck was so smooth, and my co-driver kept having to remind me to keep to the left to avoid scratching it on the trees.

Even some 4×4 instructors were eager to test the rig’s limits

Towards the end of the course, it split off into two parts: to the left was an easy, obstacle-free incline. It was steep, but nothing was there to make it difficult. To the right was a rocky, uneven surface that required a spotter to clear. My co-driver, Alli, said to me, “I don’t think they’ll take this over the hard section; this truck’s pretty big.” We were both shocked when the instructor directed us to go to the right. We looked at each other, eyebrows raised, and headed to the right. Like the other section of the course, it was nothing for this truck. I followed the hand signals of the instructor and made it over the difficult section in seconds, without feeling like our organs were displaced. 

Then we climbed the final hill, did a few more rocky sections to master throttle control and wheel placement, a steep decline, and then exited the course. Overall, it took about 15 minutes, and every second felt like an hour, but it was an amazing experience. After doing the course in my Jeep, I felt much more in tune with my TJ and walked away a more confident driver.

Final thoughts

I thought driving a truck the size of a small village was going to be much more of a challenge. But modern technology, a powerful engine, mods that improved its capabilities, and a trove of instructors helped me realize the GMC 2500 HD AT4X was made to tackle obstacles like the ones I encountered on the Overland Expo PNW’s off-road course. Engineers likely tested these trucks on similar or even more difficult obstacles to refine the AT4X’s abilities. 

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. The second day is when people drive on the course in their own off-roader, with an instructor at every turn to ensure you’re taking the turns correctly, in the correct gear, etc. It’s a great way to get to know a vehicle and how it’s best used before you risk damaging it in a real-life scenario. In my opinion, it’s $75 well-spent.