2021 GMC Sierra 1500 AT4 Road Test and Review

When it comes to trucks, it seems as though everyone wants the lifted off-road look. That’s why the 2021 GMC Sierra AT4 exists. In addition to a custom appearance with body-color bumpers, grille, and trim, the Sierra AT4 adds a 2-inch suspension lift for extra ground clearance, off-road shocks, skid plates, mud-terrain tires, and purposeful red front recovery hooks. Equipped with a two-speed Autotrac transfer case and a locking rear differential, it’s ready for rugged terrain right off of the assembly line.

The AT4 is just one of five different Sierra models you can buy. The truck also comes in SLE, Elevation, SLT, and luxurious Denali trims. Depending on which one you choose, you can get a regular cab with a long bed, an extended cab with a standard bed, or a crew cab with a standard or short bed. Our AT4 test truck was loaded with extras, including Premium, Technology, and Preferred option packages; a 3.0-liter turbodiesel six-cylinder engine; a CarbonPro carbon fiber composite cargo bed; and more. The price came to $66,595, including a $1,695 destination charge.

When you shop for a 2021 GMC Sierra 1500, you’ll choose between standard, SLE, Elevation, SLT, AT4, and Denali trim levels. Regular cab Sierras come only with standard trim; extended cabs offer standard, SLE, and Elevation specifications; and crew cabs are available in every Sierra flavor.

With the SLE trim, the Sierra looks and feels like something more than a basic work truck. You get chrome exterior trim, aluminum wheels, GMC’s fancy MultiPro tailgate, and a more comfortable cab with extra amenities and more technology. Elevation trim builds on this with body-color and blacked-out trim and black 20-inch wheels. Choose the SLT for additional cosmetic, functional, and premium upgrades. The SLT also comes with standard leather upholstery and provides greater access to optional equipment, including helpful towing technologies. The Sierra AT4 builds on the SLT with its off-roading equipment. The Denali represents the top-of-the-line Sierra. Design-wise, it borders on gaudy, but that doesn’t prevent truck buyers with fat wallets from choosing it. Still, you’d be surprised by what’s optional for this version of the Sierra. Like paint, for example. And a forward-collision warning system with automatic emergency braking. 

Styling sells the GMC Sierra. After all, it’s basically the same thing as a Chevrolet Silverado, but it costs more money. But with its big grille, blunt nose, and bulging fenders with asymmetrical wheel arches, the Sierra has what many people might consider a more appealing look.

Inside, the Sierra and Silverado are essentially carbon copies of one another. On the one hand, the industrial-grade design and execution are befitting of a truck. But on the other hand, modern expectations dictate durable materials and purposeful design that doesn’t necessarily look and feel that way. The control layout is sensible, though, with numerous buttons and knobs to reduce interaction with the infotainment display screen. You can easily find what you’re looking for in this truck, though using some of the controls while wearing gloves is a challenge.

Five adults easily fit into the Sierra AT4, and though they aren’t large, the side step rails come in handy, especially for shorter people. Once everyone has clambered aboard, they’ll enjoy plenty of head and legroom. The test truck also had heated and ventilated front seats with a wide range of power adjustments and a heated steering wheel. Perhaps appropriately for the AT4, the seat leather is quite stiff, looking and feeling durable instead of upscale. After a few hours in the saddle, the driver’s seat feels like one. A massage function would be great.

Rear-seat passengers enjoyed the test truck’s heated rear cushions and its large air conditioning vents. Interior storage space is good but not quite as innovative or well-executed as the competition. GMC embeds hidden compartments into the rear seatbacks, but they don’t lock, so be mindful of what you store in them. Cargo bed volume is class-leading. With the Sierra’s standard corner-step bumpers, available MultiPro tailgate, and optional carbon fiber composite CarbonPro bed, this GMC is competitive when it comes to one of the reasons you’re buying a truck in the first place.

The Sierra’s infotainment system doesn’t look very impressive, but it is competitive in terms of features and functionality. All it needs is a bigger touchscreen display to keep up with what Ford and Ram are offering.

Every Sierra includes Bluetooth pairing for two devices at the same time, Apple CarPlay, and Android Auto. Upgrade to the SLE, and you can subscribe to GMC connected services, including a 4G LTE Wi-Fi hotspot. The SLE Preferred Package adds wireless Apple and Android smartphone integration, SiriusXM 360L satellite radio, and HD radio for a nominal fee. Beyond this, navigation and a Bose premium sound system are also available. GMC needs to step up its game when it comes to high-end audio, because the test truck’s Bose components are unworthy of a truck priced over $65,000. Otherwise, the infotainment system works well, especially its voice control technology. During testing, local power outages demonstrated how valuable the Sierra’s Wi-Fi and in-dash household-style power outlet can be.

Many people don’t want driving assistance technology forced upon them, which might be why GMC makes the Sierra’s available features optional — even on the top-of-the-line Denali. Those days are likely coming to a close, though, and soon. Rumor has it a refreshed 2022 Sierra will even offer Super Cruise, a hands-free highway driving technology. So if you want a truck without all of these opt-in gewgaws, act sooner than later.

Our test truck had all of the available advanced driving assistance systems, and they worked pretty well. Accurate and smooth, the tech in this GMC reflects the advancements its parent company, General Motors, has made regarding this technology. Unfortunately, the GMC Sierra’s crash-test ratings fail to impress. It does not earn the highest overall rating from the National Highway Traffic Safety Administration, and it receives a Marginal rating in an important crash test conducted by the Insurance Institute for Highway Safety. Plus, the IIHS says the headlights are Poor.

If you buy a new GMC Sierra, you absolutely must consider paying $995 extra to upgrade from a V8 to the excellent 3.0-liter turbodiesel inline six-cylinder engine. This Duramax diesel is an absolute gem and a genuine bargain.

Horsepower measures 277 at 3,750 rpm, which isn’t all that impressive. Torque is this engine’s talent, and it whips up 460 lb-ft of it starting at just 1,500 rpm. As a result, the Duramax supplies a steady stream of thrust, helping the Sierra to feel powerful and responsive. Better yet, it effortlessly returned 21.1 mpg during a test drive that included a run from sea level to nearly a mile of elevation. That’s less than the EPA’s official rating of 24 mpg, but under the circumstances, it met expectations. GMC uses a 10-speed automatic transmission with this engine, and the AT4’s Autotrac two-speed transfer case makes it easy to run the truck in 2-wheel drive, automatic 4-wheel drive, 4-Hi, or 4-Lo. Our test truck could tow 8,800 pounds and haul 1,810 lbs of payload. Maximum ratings with the Duramax, depending on truck configuration, are 9,300 lbs and 2,150 lbs, respectively.

One of the best things about the Sierra AT4 is its ride quality. The Sierra can feel too soft and woozy at higher speeds in standard specification, but the AT4’s off-roading suspension cures that problem. The truck isn’t firm in the sense that it will beat you up on lousy pavement (or off-road), but it certainly does a better job of attenuating unwanted body motions.

What GMC giveth, though, it also taketh away. The mud-terrain tires are not optimized for pavement driving. They whir loudly on the highway. And on a winding country road, they offer little in the way of grip. They excel, however, in the mud. And on terrain. Following spates of rain, we ventured off-road. The Sierra AT4 seemingly chuckled at the challenges we presented to it, shrugging off the ruts, the mud, and the rocks along the trail. You might buy the AT4 for its rugged good looks, but you’ll wind up loving it for its ride on pavement and its handling off of it.

The GMC Sierra AT4 is basically the same thing as a Chevrolet Silverado Trail Boss. Alternatives outside of the General Motors family include the Ford F-150 Tremor, the Nissan Titan Pro-4X, the RAM 1500 Rebel, and the Toyota Tundra TRD Pro. Each of these trucks offers factory-backed off-roading upgrades covered by the original equipment warranty.

Granted, you might want to custom-tailor a truck to personal preferences, ensuring your rig is one of one. But when you do that, you can throw off the calibration of safety technologies while voiding your warranty. If that doesn’t matter to you, there is no shortage of aftermarket companies ready, willing, and able to create exactly what you want. All it takes is money.

Of all the 2021 GMC Sierra configurations, the AT4 is my favorite. It tones down the Sierra’s exterior chrome, adds a purposeful stance, and delivers an excellent on-pavement ride combined with serious off-road capability. Plus, the optional Duramax diesel is nothing short of delightful and an absolute bargain compared to what Ford and Ram command for their diesel-powered V6 engine options.

However, the Sierra’s safety ratings aren’t competitive, and the safety technology is optional rather than standard. The interior looks old and feels cheap. And the premium sound system is anything but. GMC also charges half the Duramax’s price for metallic paint and offers shorter free trials of connected services than competitors. Overall, there is room for improvement here. And it is probably coming in 2022.