Big trucks are more capable than ever before, and they have the payload to haul more than a few passengers and a basket of groceries. Adventurer, Scott Brady, explains to Skyblue’s readers how he outfitted his GMC Sierra AT4 Diesel into the ultimate overlanding rig.
I recently had the opportunity to discuss the features and capabilities of the GMC Sierra AT4X with Scott Brady. Scott Brady is the CEO and publisher of Overland Journal and ExpeditionPortal.com, a vehicle-dependent expedition community and overlanding resource. He has worked closely with the GMC team over the last couple of years to outfit his 2021 GMC Sierra AT4 Diesel into the ultimate overlanding vehicle and has documented the build process along the way. We also discussed his thoughts on the new 2023 Sierra AT4X and the AEV edition.
Migration to larger heavier duty trucks, more payload
Full-size trucks are now the vehicle of choice for North American overland travel, with robust payload and towing capabilities. The main reason for this trend is the shape of the mid-sized offerings, which provide less payload than some sedans. Full-size trucks have better durability too, from stronger frames, larger drivetrain components, and more effective cooling. Even so, they are also well-appointed and comfortable for the long-distance traveler. Full-size trucks do have their downsides: they’re wider and longer than other trucks, which complicates some trail access.
Scott Brady wanted a bigger truck with more payload for his overlanding adventures to allow him to carry more gear and travel further into the wild. So in 2021, he decided to go with the half-ton GMC Sierra 1500 AT4 with its 3.0L Duramax Turbo Diesel Engine diesel engine (only available in the AT4 trim) and 10-speed automatic transmission. He finds that the Duramax engine in his GMC Sierra AT4 provides a long range and a high power output, making his truck perfect for long trips in remote locations.
He notes that his engine is especially impressive: the Duramax engine at only 40 percent the displacement of the 7.3 makes 277 horsepower and 460 pound-feet, all while delivering a best-in-segment 30 mpg. With the standard 24 gallon fuel tank, Scott’s Sierra AT4 is capable of traveling 700 miles on a full tank. This is very useful when you are traveling down the long axis of Greenland or circumnavigating the globe.
The GMC diesel engine requires ultra-low sulfur diesel, which Scott finds he can get from places like Northern Mexico, Canada, and the USA. He notes that diesel fuel has a higher flash point than gasoline; this makes it less volatile and safer to carry around because it is less flammable.
Equipped For Adventure
When asked about why he chose the Sierra AT4, Scott explains that one of his key factors was good trail performance. The AT4 provides a 2-inch factory lift and Rancho shocks, along with a mechanical locking rear differential and additional skid plates.
At first, Scott was slightly intimidated by the size of the vehicle on the trail. He spent his first few test drives moving a few feet at a time on a test track, getting out to look at all the clearances. To his surprise, even his most challenging test track was not an issue, and he had clearance to spare. Scott ordered the longest AT4 model available to accommodate a Scout Camper, so that put the wheelbase at 157 inches. He notes that he does notice it on switchbacks and during breakover events.
The design philosophy of the AT4 takes off-road capability to the next level with adventure-ready equipment to tackle the challenges of the trail. Key features include:
- 3.0L Duramax Turbo Diesel Engine or Available 6.2L V8 Engine with 10-speed Automatic Transmission
- 2″ Factory Lift with Off-road Suspension and Rancho® Monotube Shocks
- 2-Speed Autotrac Transfer Case, Automatic Locking Rear Differential and Underbody Skid Plates
Scott’s Sierra AT4 Modifications
While the Scott found the Sierra AT4 to be impressive in stock form, he made some modifications and personalization to the truck for his first phase of upgrades. The goal for this phase was to install a Scout Kenai camper, and provide support systems for remote backcountry travel. He also wanted to improve suspension performance and increase ground clearance.
Scott chose the Kenai model camper because its the biggest and full-featured member of the Scout family. It remains true to its values: minimalist, lightweight, and off-grid capable. Sleeping 4-6, weighing only 1,265 lbs, the Scout Kenai is a very practical truck camper. The Sierra AT4 can carry up to 2,200 pounds of payload, which is more than sufficient to carry the weight of the new Scout Kenai model, but the stock valving on the Sierra’s Rancho shock is too light for Scott’s needs. Scott has therefore installed new front coil-overs and rear shocks.
As a testimonial about the towing capacity of the 3.0L Duramax Turbo Diesel engine, Scott notes that after adding the Scout Camper he pulled a sailboat in the mountainous terrain while returning from a trip to Mexico and the truck did great.
For those wanting to outfit their stock GMC Sierra AT4 for overlanding and camping, the best practice is don’t go over gross vehicle weight. Scott notes that the AT4 is best suited for a Go-Fast GFC Platform Topper. The GFC will hold just about anything you throw on it and won’t rattle apart when you use it. With it’s 800-lb roof load rating (with 4 crossbars), you can still add additional payload and gear. If you go with the lightest weight Scout Camper, you can’t add payload without going over the vehicle’s gross vehicle weight rating. Scott notes that you can remove other items to reduce weight, like the rear payload door, for example.
Sierra AT4X: the new peak in premium off-roading
We then discussed the AT4X trim level, which gives you absolutely every functional upgrade possible. The Sierra AT4X is a balanced execution that delivers advanced off-road capability when called upon without compromising the on-road comfort, tech, towing, and payload capability expected from a premium pickup.
- Standard 6.2L V-8 engine and 10-speed automatic transmission
- Unique Multimatic DSSV spool-valve dampers
- Unique springs that, with the Multimatic dampers, increase maximum front and rear suspension travel by 50 mm and 25 mm, respectively, compared with the standard AT4 suspension
- Two-speed transfer case, with selectable modes for different off-road conditions — including Terrain Mode, which allows one-pedal3 rock crawling
- Front and rear e-locking differentials, a combination not offered by any other competitor in its class7
- Specific off-road chassis and suspension calibrations
- Unique, larger steel transfer case shield
- 18-inch black wheels with LT265/70R18 Goodyear Wrangler DuraTrac Mud-Terrain tires
- Available rocker guard accessory
Scott notes that what’s unique about the AT4X is its long travel suspension. The Sierra AT4X comes standard with the two-inch lifted suspension from the factory. This means it’s fitted with longer control arms, that are supported by Multimatic™ spool-valve dampers. The AT4X is also lifted another inch, for a total of three additional inches above the base Colorado. The top-end GMC is fitted with mechanical lockers on both the front and rear axles. Another nice feature are the standard protection parts that endow the AT4X with heavy duty steel skid plates, rock sliders, and front and rear bumpers. The front bumper can also be fitted with a winch.
A long travel suspension is something you would normally have to replace most of the parts on a truck. This includes shocks, control arms, springs etc. It also includes some things that you might not think of like tie rod ends, CV axles and new fenders. The cost can easily exceed $10,000 and decreases the mileage interval between major suspensions.
Customers who buy midsize trucks often have to add aftermarket parts themselves to get the features they want. Adding these parts piecemeal to other trucks creates problems with integration because third-party parts often interfere with factory safety sensors. Furthermore, many of these customizations invalidate the vehicle’s warranty. Scott notes that GMC’s Multimatic™ suspension is “an exceptional feature to have in a stock vehicle.”
Another point that Scott makes is that “GMC’s AT4X has the best shocks ever in a pickup, be it on or off road. They were developed with technology from Formula 1, and it shows.” GMC has an exclusive arrangement with Multimatic™ to bring their DSSV Spool-valve Dampers in the AT4X’s shocks. Multimatic’s race-proven spool valve dampers are featured on select high performance production vehicles. Multimatic moved the spool valves that control on-road ride into a chamber in the middle of the damper and placed a third spool valve on the shaft in the main body that handles extreme compression events. What it created is a bypass shock that doesn’t compromise on-road handling for off-road comfort.
This suspension system is 2-inches higher (in terms of suspension travel) than other Sierra trim levels. Scott further explains that the Sierra AT4/AT4X are long travel vehicle without being a wide track. This is a benefit over the RAM TRX and Ford Raptor, which are wide-body trucks, best suitable in open desert. AT4X is standard body width that can fit into narrow mountain trails.
2023 Sierra 1500 AT4X AEV Edition
Before we finished our interview, I asked Scott for his thoughts on GMC’s new 2023 Sierra 1500 AT4X AEV Edition, which was recently revealed at Overland Expo Pacific Northwest near Bend, Oregon. Scott explains that the new AEV Conversions edition GMC AT4x is “an impressive new factory overlander, with a winch-capable front bumper, F/R lockers, 2” lift, 33” tires, AEV steel rear bumper, Multimatic™ shocks, boron steel skid plates and more.”
The new 2023 Sierra 1500 AT4X AEV Edition is the most off-road capable factory Sierra 1500 ever. Updates include:
- AEV stamped steel front and rear bumpers with heavy duty recovery points and winch capability (front bumper)
- Five hot-stamped boron steel skid plates (front approach, steering gear, transfer case, fuel tank and rear differential)
- Unique, race-inspired, laser-engraved 18-inch AEV Salta wheels in gloss black finish with AEV’s signature recessed valve system for added protection from rocks on the trail
- 33-inch Goodyear Wrangler Territory MT tires
- Updated front grille and fascia to accommodate the new bumper and larger tires, gloss black door handles and a black contrast inner tailgate
- Exclusive AEV branding throughout the vehicle, including on bumpers, embroidered head rests and all-weather floor liners
- Available off-road rocker panel protectors to help shield the sills and frame rails and an optional bolt-on step assist when not off-roading
In his experience, aftermarket parts will never interface completely with the rest of the truck the way a stock part would. All of the equipment is designed to work together. That means you won’t have to do any complex tuning of the parts, and they’ll all have the same level of weather resistance and long maintenance intervals that you can expect from a factory component. It’s a better solution in every way.
Scott then explained that when purchasing a truck, it is important to find a vehicle that will be reliable for the job. In other words, find the right tool…
Skyblue Featured Video: Scott Brady’s 2021 GMC Sierra AT4 Overland Project with Scout Camper
About Scott Brady
Scott Brady is the publisher and co-founder of Expedition Portal and Overland Journal. His travels by 4WD and adventure motorcycle span all seven continents and include three circumnavigations of the globe. His polar travels include two vehicle crossings of Antarctica and the first long-axis crossing of Greenland. He lives in Prescott, Arizona IG: @scott.a.brady Twitter: @scott_brady.
With a strong foundation of manufacturing trucks since 1902 and now selling in a dozen countries across the world, GMC offers purpose-built vehicles designed and engineered to the highest standard. From the all-new compact SUV Terrain to the Sierra HD, our trucks and crossovers deliver GMC’s signature combination of intuitive technologies and premium execution, with the popular Denali representing the pinnacle of GMC design, performance and amenities. Details on all GMC models are available at www.gmc.com.
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