The GMC Sierra HD AT4X is an impressive truck. On an hour-long loop around the XOverland Ranch in Montana, I took one through slick sand, down a 29-degree loose shale descent, and over sandy hills. The AT4X handled everything well. The only downside is I spent the entire time looking through its central touch screen.
The Sierra HD is huge. The same is true for all of its competitors. The modern HD truck market demands a stratospheric towing figure, room for five to six adults, plenty of bed space, and a big, powerful engine for all that tugging. Plus, now people clamor for off-road ones like the AT4X, with meaty Mud-Terrain tires and a factory lift. The result is a hood that is up to the chin of your favorite 5-foot 6-inch auto writer. Total vehicle height is 82.6 inches, 5.5 inches taller than a 2010 Sierra HD. The AT4x is also ten inches longer than a crew-cab, short-bed 2500 from 2010, two inches wider, and a couple thousand pounds heavier. Total curb weight is up to 8605 lbs for the diesel. For an off-roader, the truck is just plain big.
GMC isn’t alone here. The AT4X has a Chevy cousin, a crosstown rival in the F-250 Tremor, and an established competitor in the segment-original Ram Power Wagon. For city dwellers like myself, it’s easy to assume that these trucks are totally beyond reason. Sitting in suburban California, I can absolutely imagine needing the capability of a locking rear differential, 35-inch tires, skid plates, and DSSV dampers, and I can imagine needing 18,500 lbs of towing capacity. But it’s hard to imagine needing both in one truck.
Out testing in Montana, though, it’s hard to pass a single rural house without seeing an HD truck and multiple things that necessitate one. Plenty of Americans have skid steers and construction equipment, horses or campers. Many of them also live in places like Montana, where we saw six inches of snow on the ground in October. HD trucks with maximum off-road capability make sense for some.
You just can’t see out of them. With that tall, long hood stretching out in front of the windshield, the HD AT4X blinds the driver. It’s hard enough to see out of a mid-size trail rig. In the Sierra HD, you have such a large blind spot in front that it’s tough to place your wheels with confidence. Any positive incline makes it completely impossible. From what I hear, the same is true in the Power Wagon or F-250.
The manufacturers know this is impossible, so they all outfit their HD trail trucks with plenty of cameras. The Sierra HD AT4X has one pointing in every direction, with multiple ways to configure them. There’s a front camera (essential to see out), side cameras, a digital wide-angle rearview mirror, and more. It’s also got wiring for additional cameras should you add them yourself. The underbody camera from the GMC Canyon AT4X springs to mind as a good option.
More angles are good, because the camera system is how you drive an HD truck off-road. Experts may roll their eyes at this point saying they pilot 3500s up trails all the time, but unless you know the trail and the truck perfectly you’re going to need plenty of visual assistance. The good news is that the cameras work. The bad news is that you have to rely on them almost completely.
If you do, you’ll find the AT4X has excellent approach and solid departure angles (31.6 and 25.7 degrees, respectively), but the length of a modern HD truck also exacts a compromise. The maximum breakover angle is 21.2 degrees, which means if you struggle to clear an object, it’ll probably snag on the truck’s midsection. Again, I reference the Canyon’s underbody camera. With trucks this big, you can solve a lot of problems with just one more camera.
Arguably the most fickle member of the Road & Track staff, Reviews Editor Mack Hogan is likely the only person to ever cross shop an ND Miata with an Isuzu Vehicross. He founded the automotive reviews section of CNBC during his sophomore year of college and has been writing about cars ever since.