Building on top of the all-new 2020 GMC Sierra 2500HD, the revamped 2021 GMC Sierra 2500HD retains much of the character from the 2020 model year, while adding more high-tech features that make the $78,000 as-tested price for the Denali trim more than worth it.

At the heart of our Sierra was the 6.6-liter Duramax V8 turbodiesel that sold us on the truck. The L5P diesel engine is the clear choice for towing capacity as well as for the Allison 10-speed transmission that it pairs with. Combining 910 pound-feet of torque and 445 horsepower to the smooth and strong Allison transmission was exactly what a truck this size needs. The Duramax engine, built in Ohio, is quiet and powerful. The L5P engine first appeared in 2017 and has not changed since then, which has allowed the competition to close the gap.

Even by modern standards, the truck is extremely large, towering at nearly 6’8” tall. As a driver, you feel in command of the road, even when near large semi-trucks. Behind the wheel, all you see is the giant hood, which is made even bigger with the built-in hood scoop. The driving experience is new for 2021 with wireless Apple CarPlay and Android Auto capability that is seamlessly integrated into the 8-inch premium infotainment system as well as enhanced camera trailering technology that was extremely helpful when towing. The infotainment system is as easy to use as they come in modern vehicles, and was as intuitive as it was informative. The heads-up display was great for keeping focused on the road ahead. However, the color scheme of the cluster made it difficult to make out at times. The secondary gauges don’t have needles but instead rely on a blue fill on a black background that is hard to see. It is especially difficult to see the fuel gauge when it is lower than a quarter tank.

Towing with the 2021 GMC Sierra 2500HD was a great experience. Beginning with the helpful Trailering menu on the infotainment system, which made testing trailer lights an easy and painless process, something that isn’t always the case. Once on the road, it is apparent that the Duramax diesel has enough power and torque to pull almost anything. Our 2500HD model had a conventional towing capacity of 18,500 pounds. However a similarly equipped 3500HD model is rated for 20,000 pounds conventional and up to 36,000 pounds gooseneck. Clearly, the Duramax engine can pull large loads like a train, but to do so you will need the stiffer chassis and suspension that the 3500HD can offer. However, for most towing needs, the 2500HD is more than enough, and only the most hardcore towing will highlight the difference between the 2500HD and 3500HD. During our testing, we managed 17 mpg combined with no payload and 10 mpg while towing, a testament to the efficiency of the Duramax engine. Combined with the 36-gallon fuel tank, stops could be over 600 miles apart, which was not a problem considering the luxurious interior that has every amenity you could need.

The Denali luxury experience is fantastic and really makes it possible to use this truck on work or pleasure trips with ease. Passengers can plug in laptops and tablets to the onboard 12-volt plugs and take advantage of the high-speed Wi-Fi that has no problem keeping up with the needs of multiple devices. The seats are definitely not out of a sporty roadster and were a bit too wide for our liking. Some more support would have gone a long way.

Night time driving was no problem thanks to GMC’s excellent headlights that were extremely bright and well-adjusted to maximize visibility. Rearward visibility was aided by large retractable side mirrors that helped improve the towing experience. As much of a gimmick as GMC’s MultiPro Tailgate might seem, it has many practical uses such as a step, which is needed with a truck this size, or a bed extender. If tailgating is your thing, the integrated tailgate speakers are a must-have. As with many four-wheel-drive trucks, the ride was on the harsher side compared to lighter duty two-wheel-drive options.

The 2021 GMC Sierra 2500HD Denali is exactly what we were hoping for, a rugged four-wheel-drive truck that can haul just about anything while offering a luxurious, spacious, and comfortable interior that blends technology with practicality. It is powerful, fuel efficient and can eat up miles with ease.


Engine: 6.6-liter Duramax turbodiesel
Horsepower: 445 @ 2,800 rpm
Torque: 910 @ 1,600 rpm
Front Suspension: Short/Long Arm independent with torsion bars
Rear Suspension: Semi-elliptic three-stage multileaf spring
Transmission: 10-speed Allison automatic
Axle Ratio: 3.42:1
Curb Weight: 7,430 lbs.
Base MSRP: $76,945
Image courtesy of General Motors

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