2021 GMC Sierra 1500 AT4 Duramax Diesel

GMC Sierra 1500 AT4 Duramax: The Unintended Review

This GMC Sierra came in for review under an interesting premise. In fact, I wasn’t even looking to review it exactly. I was working on a review for another publication for the Smittybilt air compressor and needed something with larger tires to test it on.

When I reached out to one of the companies that supply press cars in the Detroit area to come by their place and run a quick test, they offered to leave the GMC for a week. Good with me, I haven’t had a chance to try out the straight-six Duramax Diesel yet.

2021 GMC Sierra 1500 AT4 Duramax

Given that the last half-ton truck I reviewed was the Ford F-150 with their new PowerBoost engine, I was interested to see how well the diesel stacked up against a hybrid for drivability and fuel economy among others. Too, I was interested to see if the GMC interior was better than the Chevy Silverado I tested a couple of years back when this generation of GM half-ton trucks debuted.


The first thing that strikes you about this AT4 trim level Sierra 1500 is its physical size. The hood line is over four and a half feet high. The roof of the truck is nearly seven feet high. Perhaps a tired trope but it’s true, this half-ton truck is the size of 3/4 ton and 1-ton trucks from just a few years ago.

The styling of the truck is handsome, it’s far more successful than the Silverado. It comes off as athletic rather than overly macho. The AT4 package brings among other things, a two-inch lift, heavier duty shocks, skid plates, and Goodyear Wrangler tires that are just shy of 33 inches tall.

The multi-function tailgate has been around for a few years now, and it set off the “tailgate wars”. Though I’m sure, Honda would say the tailgate on the Ridgeline was the one that actually started it. Still, the GM tailgate is well executed and has useful purposes rather than being a marketing gimmick.


Step up into the cabin of the GMC and it’s not the embarrassment that the Silverado was. That said, there are several areas ripe for improvement. There is still plenty of hard plastic around, though far less than the Chevy. It’s a truck so it needs and wearing parts, but this is the “professional grade” truck, not the baseline work truck. The materials have a better look, and in places a better feel, but Ford and Ram still do a better job with their materials.

The driver’s seat is quite comfortable and you should be able to do long miles in this truck very easily. Given the larger off-road orientated tires, there isn’t any tire noise that makes its way into the cabin. The cabin is rather quiet and well sealed from wind noise. It is not a luxury car quiet but it is very good.

The rear seat room is enormous. It has half an inch MORE legroom than a Bentley Flying Spur. Think about that for a moment. The rear seats do flip up and there is storage underneath them, though I wouldn’t leave anything valuable there. Too on the driver’s side, a portion of the back part of the seat hinges down to reveal even more storage space.

Also good is the lack of engine noise. The 3.0-liter Duramax Diesel is a very refined unit. There is no clatter from the injectors. There is a general lack of harshness coming from any mechanical noises of the engine at all. You’d be hard-pressed to tell at startup or even under acceleration that you are driving a diesel-based on engine noise.


Ram and Ford also offer much larger infotainment screens at their higher trim levels like this AT4. Where Ford and Ram are offering 12+ inch screens/tablets, the GMC has an 8-inch screen. Problem is, it doesn’t even appear that large given how expansive the dash is in the truck.

One other annoyance with the infotainment stack is a lack of physical buttons. Yes, it has a volume and tuning knob, but it lacks a few key other ones. Given the physical size of the truck, and how high the hood is, it can be difficult to place in tight parking spaces. Or even spaces that aren’t that tight. The Sierra has plenty of cameras for helping guide you in and around parking spaces. However, there is no physical button to trigger them when you are trying to maneuver. You have to go several layers into the menu system in the infotainment system to trigger them on.

That somewhat major gripe aside, the standard UX for GMC’s infotainment is very good, and if you prefer Sierra offers wireless Apple CarPlay and Android Auto. The screen itself is responsive and very quick as you swipe between screens or select items on the on-screen menus.

On The Road

Maybe the two most important things people want to know with a truck like this are (a) how does it tow, and (b) how does it do off-road. I can’t answer either of those questions. The person with the enclosed race car trailer was out of town at a race, and I didn’t have time to head up to the off-road park to go play.

That out of the way, as a daily driver, the Sierra 1500 is fine. Given the 32.5 inch tall tires with the generous sidewall and the extra suspension travel, it soaked up all the large potholes around the Metro Detroit area with ease. Given those tires, I didn’t have to worry about sharp edges on the potholes which are known for tearing many a sidewall around here.

As large as this truck is, it is not the easiest to get in and out of parking lot spaces. The wheelbase is 157.1 inches, the overall length is 241.3 inches (that’s 20 feet long!), and 81.2 inches of width. You will find yourself getting in your daily steps as you park away from everyone else just to make it easy to get in and out of space.

On surface streets, the Sierra takes up most of the lane. When you’ve been driving smaller vehicles for several weeks, it’s slightly unnerving in tight traffic. About the time the truck when back I was almost used to it. On the highway, the ride is luxury car good and nearly that quiet. You hear zero clatter for the diesel engine. As mentioned earlier you hear almost no noise from the engine at all.

Acceleration from a standstill is good, but it will not put you back in your seat. Even though this Duramax diesel puts out 460 lb/ft of torque at 1,500 rpm, the truck still weighs over 5,300 pounds. Once rolling, if you tip into the throttle it will move nicely.

Final Thoughts

When it comes to pickups brand loyalty is everything. If I was in the market for a half-ton truck this GMC and the Ram would be at the forefront of my choices. Why? Because you can get them with a diesel. Ford has just dropped their diesel option in the F-150, so for me, it is not an option. Why a diesel? Because it offers better fuel economy day today. It offers better resale down the road. If you are towing it’s a better and safer experience. The upcharge is for the GMC is less than choosing the 6.2-liter gas engine! What’s not to like.
Overall this is a good truck that if you buy it will serve you well for ten plus years and a couple hundred thousand miles. Yes at $63,360 it’s very expensive, but you are very hard-pressed to get any half-ton truck to sticker under $50,000 these days. I like the interior of the Ram better, and I think the F-150 has a slightly better interior but after that, go drive them all and buy what you like.

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5 responses to “GMC Sierra 1500 AT4 Duramax: The Unintended Review”

  1. outback_ute Avatar

    The lack of a button for the around-view cameras is pretty ridiculous.

    How did the fuel consumption go compared to the hybrid Eric?

  2. crank_case Avatar

    Duramax sounds like a heavy duty contraceptive product for someone that really can’t afford another kid.

    1. Tiller188 Avatar

      “When you have to give it to her all night long, and can’t afford any ‘accidents’…Duramax. There is no substitute.”

  3. Slow Joe Crow Avatar
    Slow Joe Crow

    I’m glad GM is moving away from the massive slab front like the lifted Chevy 3/4 ton I saw yesterday. It appears they also went to a full 6′ bed since your tester is on a 157″ wheelbase, the same as my 8′ bed F150 Supercab. I appreciate the bed length but parking can be a challenge. Fortunately I live in a semi-rural area so Wilco and Lowes have extra long parking spaces. I also have a two wheel drive truck so my turning circle is tighter than 4×4 and I can easily see all four corners without resorting to cameras, although a camera on the back would be nice for hooking up trailers.

  4. Tanshanomi Avatar

    I don’t think I realized how completely and unnecessarily the Silverado was ruined by it’s horrendous grille. I had thought it was thoroughly ugly, but this is unobjectionable looking, borderline attractive.

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