Testing trucks is always fun. Well, to be honest, testing any vehicle is fun and is absolutely a privilege, but I absolutely love putting trucks through their paces. My most recent tester was the 2021 GMC Sierra 1500 AT4, a factory off-road model with style and substance. Let's take a look at what makes it tick.

Off-Road-Ready Truck With a Stout Powertrain

Key upgrades here include a two-inch factory lift kit with Rancho Monotube Shocks, Goodyear Mud-Terrain tires mounted on 20-inch wheels, a two-speed automatic transfer case, and a traction select system with off-road and towing settings.

The net effect of all that gear is impressive. The AT4 rides as smoothly as many crossovers and maneuvers with relative ease for a truck its size. In town, there's little distinction in driving manners between this beefy off-road pickup truck and most family haulers, as long as being taller than nearly everyone else in traffic is ok with you. The truck handles well, and exhibits little instability over bumps at speed, which is a common challenge with pickup trucks and off-road vehicles.

My test truck was equipped with the optional 3.0-liter Duramax turbodiesel and a ten-speed automatic gearbox. With 277 horsepower and a stout 460 pound-feet of torque, it's the perfect companion for a truck meant to climb over and out of gnarly obstacles on the trails. In daily driving scenarios, the engine is quiet and refined, and shows little of the rattly, noisy diesel sound many people expect from the engines. With plenty of torque on tap, the AT4 feels somewhat lively, and is able to navigate traffic with ease. Reaching highway speeds and passing once there is also a breeze, and the truck remains surprisingly peaceful on the interstate.

Comfy Interior and Useful Bed Features

Inside, my test truck came equipped with leather upholstery and optional heated/cooled front seats. We had a rare heat wave in Maine during my week with the truck, and its powerful air conditioning combined with the cooled seats to create a much-needed oasis for this rare brutal week in northern New England. The front seats are wide and well-padded, but I found myself shuffling around, wanting more in the way of hip and thigh support. There's a tendency to slide to one side of the seat and stay there, which could easily be solved with a bit more bolstering on both the seat back and bottom.

The Sierra's cabin is comfortable and well-made.GMC

As all of my vehicle testing adventures do, the week with the AT4 involved plenty of kid transport. The full-size pickup's back seat is wide and flat, which makes it ideal for installing car seats, but I can't imagine that it'd be extremely supportive for an adult over a long-haul trip. The truck's lift means it's hard for kids to climb in, but they had a fun time trying. The novelty may wear thin over time, but it lasted for the week we had the AT4. Once inside, the kids (and anyone else in the back seat) had their own air conditioning vents and plenty of room to stretch out in their booster seats.

Normally, a truck bed would be an afterthought in a review, but GMC has gone to lengths to make its bed a standout. The Carbon Pro composite bed material is tough, as in there's no need to worry about throwing whatever you want into the bed tough. I hauled over 100 30-pound patio paver blocks over the course of a few trips, and never felt the need to add extra protection to the bed after the first trip. I tossed an old rug and some flat cardboard to protect the bed at first, but it proved to be as stout as GMC claims. Adding functionality is the MultiPro tailgate, which offers several options for steps and different cargo hauling situations. It makes an excellent step, and when the center section is folded down, it opens up much more access to the bed when standing on the ground. My tester also had an optional Bluetooth speaker system built right into the step system, which would make for an awesome camping or beach party.

Tech-Heavy Cabin

In terms of tech, the Sierra AT4 is up to speed but nothing to write home about. Its optional 8.0-inch touchscreen runs wireless Apple CarPlay and Android Auto with an option for wired connections. There's also Bluetooth, SiriusXM Radio, and more. It's a cohesive system that is easy to use and intuitive, made even easier by clever behind-the-steering-wheel-mounted controls that allow volume and track adjustments. My truck also had an optional head-up display, which unsurprisingly is extremely difficult to see with polarized sunglasses. This is a common issue not unique to GMC, and could be solved by switching to non-polarized glasses.

The MultiPro tailgate adds ultimate functionality.GMC

Most advanced safety equipment is optional, and when I say most, I mean all. The Sierra AT4, and all Sierras for that matter, is available with automatic emergency braking, a bed-view camera system, forward collision alerts, front pedestrian braking, a front/rear parking assist system, blind spot monitoring, lane keep assist, lane departure warnings, and more. While I get the need to differentiate models with various features, the lack of some of these safety items is hard to swallow at nearly $60,000.

Bottom Line

I tend to become infatuated with full-size pickup trucks while I have them in for testing, but that feeling typically fades after a while. The Sierra AT4 was a little different. The diesel engine and comfortable interior make for a supremely daily-drivable pickup truck, and the Carbon Pro bed with multi-function tailgate makes a strong case for the GMC. Ultimately, it's too much truck for me, but it's a solid choice for those that can put it to work.