Power420 HP / 460 LB-FT
Curb Weight5015 LBS (Base)
Towing9,400 LBS (Max)
MPG15 City / 19 Highway
As Tested Price$57,490
But at least it looks the part as it trudges up this uncharacteristically verdant mountain with San Diego in the distance to the north and Mexico to the south. Its special, dechromed AT4 grille has a purposeful appearance, but tastefully lacks the show-off machismo of Ford and Ram's off-roading models. The red tow hooks are a nice touch and the dark-accented 20-inch wheels wrapped in all-terrain rubber are just the right size beneath a suspension that is raised an extra 2 inches from every other Sierra.
That would be one of the key elements that differentiates the AT4 as the Sierra's off-roading model – GMC's answer to the Chevy Silverado's Trail Boss trims. In fact, their mechanical enhancements are identical. Besides the 2-inch lift, the suspension features off-road-tuned Rancho monotube shocks. There's also a locking rear differential, a two-speed transfer case, skid plates and those tow hooks.
The 5.3-liter V8 with Dynamic Fuel Management is similarly standard, but unlike the Silverado Trail Boss, the Sierra AT4 offers the 6.2-liter V8 good for 420 horsepower and 460 pound-feet of torque as a roughly $2,500 option. That's the engine we have and it delivers the expected punch, complete with a satisfyingly snarling exhaust note. However, as observed in back-to-back drives with these two available engines during the Silverado launch, the 6.2 certainly isn't necessary. The 5.3-liter is seriously capable and the bigger engine is largely for those who want to have the biggest number possible emblazoned on the fender. It's overkill, which in this particular environment, is fitting.
Besides the available engine upgrade, the AT4 also goes beyond its Trail Boss counterpart by dipping into the Sierra Denali's tool box. Its MultiPro tailgate is standard equipment, allowing for six different configurations, the most notable of which include a means of more easily reaching into the bed and a drop-down step that eases entry into the bed. GMC's considerable touting of that last element is rife with hypocrisy given GM advertisements that mocked Ford's similar feature.
MultiPro admittedly has greater functionality, including a further upgrade that embeds within it a pair of speakers, rudimentary audio controls, and USB and aux inputs. It's sourced from marine applications and looks like it. Sound quality is acceptable, if a bit tinny, but for tailgating purposes, it would be a nice addition. Especially since the bed's standard 120V power outlet and that aux jack would let you plug in a TV back there, while GMC's standard 4G LTE WiFi makes it possible to stream live TV through something like YouTubeTV. Your tailgate party could now feature the pre-game show.
Another Denali bed feature is the optional carbon fiber CarbonPro bed. GMC says it offers best-in-class dent, scratch and corrosion resistance. Our AT4 didn't have it, but then we also forgot our rusty anchor at home. A test for another day, perhaps.
The Denali's bed feature content should be a clue that the AT4 (base price $52,295) is only available as an upper trim level – the Trail Boss offers base Custom and upgrade LT versions. Although MultiPro and CarbonPro are shared with Denali (along with heated and ventilated front bucket seats), the rest of AT4's standard features are actually in line with the lower SLT trim level. The Denali's other extras – standard accident avoidance tech, Bose audio system, integrated navigation system, wireless smartphone charging and 8-inch gauge cluster display – are options. You also get a vaguely carbon fiberish trim on the center console and doors versus the Denali's vaguely woodish trim, but as both are plastic, does it really matter? The Sierra cabin's quality and design continue to underwhelm, especially in an upper trim like this.
On the road, the AT4's extra height doesn't negate the new Sierra's surprisingly lithe feel. Maybe "lithe" is too strong a term, but comparatively speaking for a full-size truck, it changes direction with poise and doesn't overwhelm. A rather small steering wheel helps in this regard, as does the improved rack it's connected to for 2019.
Ride quality is also just fine given the suspension's off-road mission. Perhaps the Ram 1500 and its coil spring suspension would be obviously cushier when driven back-to-back, but in a vacuum at least, San Diego County's less-than-perfect roads didn't surface any tiresome behavior. The Denali's magnetically controlled adjustable dampers would be better still, but you also shouldn't shy away from the AT4 because of them.
And really, the AT4 should be considered an alternative to Denali. GMC certainly seems to think so, as it is spreading the AT4 trim throughout its lineup of trucks and SUVs to provide customers with a different flavor of premium trim level. Instead of fanciness and chrome, you get fanciness and ruggedness. Already, it's an approach that's working. The Sierra AT4 has proven popular among 2019 Sierra customers, staying on dealer lots only 15 days on average before being sold (a comparatively very short time).
Are those buyers likely to take advantage of the extra off-road potential? History and market trends would indicate otherwise (how often do you see dirty Jeep Trailhawk models?), but should they try, we can at least confirm the AT4 can tackle more serious terrain. Later, GMC set up a more hardcore off-road challenge with a steep rocky hill that actually challenged the four-wheel-drive and extra ground clearance. Not surprisingly, it passed with flying colors.
The most impressive take-away was actually the multiple cameras included in the AT4's Technology package, specifically the one in front, that allows you to effectively see through the monolithic hood, and successfully navigate yourself around otherwise hidden impediments. Without it, a rather nasty boulder would've taken a chunk out of that special AT4 grille. There's also an off-road inclinometer that shows the truck's current tilt and front tire angle in the gauge cluster and, if so equipped, the gigantic color head-up display.
If anything, technology like that may actually inspire those who purchase the AT4 mostly for its style to try their hands at the type of thing the truck is intended for in the first place. Hopefully they do, because overkill can get awfully boring.