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2021 GMC Sierra 3500HD Pros vs Cons

Reviewed & fact checked by
James Murdoch

Are You Considering a 2021 GMC Sierra 3500HD? Here Are Some Reasons For and Against

Big and bold, the 2021 GMC Sierra 3500HD is a heavy-duty pick-up truck that offers a good amount of towing and hauling. For years, the Sierra 3500HD struggled to compete with its stronger rivals. That is no longer the case since the 3500HD was revamped just last model year.

If you need to handle super heavy loads, then the 6.6-L diesel Duramax V8 engine is the one that you will want to get. It comes with an Allison 10-speed automatic transmission that helps the 3500HD stay within its optimal operation range. Its upgraded cooling capacity and stronger frame help this vehicle feel more capable. The air induction system and front grille were reworked last year to make everything flow a lot more smoothly.

Trailering has also become better due to the technological additions GMC made in 2020. There are now a total of 15 cameras included on the ProGrade Trailering system, one of which lets the driver virtually see through the trailer to know how it is maneuvering. This year also sees the inclusion of an optional MultiPro tailgate, which gives you six different configurations for the tailgate to help with hauling, loading, and working in general. The side bed steps and corner step bumpers are nice additions too.

The problem with the new 3500HD is that it still does not touch the more luxurious elements you will find inside of rivals like Ram and Ford. Their materials look more high-quality. Coupled with a less-than-impressive ride quality, the lack of creature comforts make the 2021 GMC Sierra 3500HD feel a bit bland.

Could this pick-up be the right truck for you? Read on to learn about what is new for 2021, what we like about the 3500HD, what we'd like to see improved upon, and how this truck stacks up against some seriously tough rivals. We will leave you with our final verdict, so be sure to read all the way to the end.

What's New for 2021?

There are some helpful new features available for the 2021 GMC Sierra 3500HD. Additions include a trailer-length indicator that warns the driver when the trailer might be too close to nearby traffic. A jack-knife alert also comes on the line-up. The MultiPro tailgate is standard on the SLE trim level and above. Three paint color options get tacked onto the list, and the Denali gains a Diamond Black Edition, 36-degree surround view camera system, and a bed-view camera. The Diamond Edition has 20-inch wheels done in black as well as retracting running boards. If you opt for the AT4, you get a high clearance step as well as mud-terrain tires to help improve its off-road oriented performance.

Ten Reasons You May Like the 2021 GMC Sierra 3500HD – The Pros

1. The Diesel V8 Engine

The best engine option in the line-up is without a doubt the diesel V8. Like the gas-only engine, it is a 6.6-L displacement, but the diesel V8 gets 445 hp and 910 lb-ft of torque. It also gets paired with last year's new Allison 10-speed automatic transmission. This engine has all the torque you could possibly need for excellent towing and hauling, far outperforming what you get from the grumbly gas-only V8. Never does the diesel come off as feeling overexerted.

2. The Allison 10-speed Automatic Transmission

The 10-speed automatic transmission introduced for the diesel engine last year is a much smarter choice than the 6-speed automatic on the gas V8. The Allison 10-speed can easily handle the 910 lb-ft of torque the diesel produces and does not spend time searching for gears. Power delivery is smooth and effortless.

3. The ProGrade Trailering System

The ProGrade Trailering system is a must-have for those who plan on hitching up their trailers. This 15-camera system will let you know exactly how your trailer is doing, whether it is staying centered or whether it is swaying toward a line. The through-trailer view you get through one camera is particularly helpful. This makes it easier for you to know how you need to maneuver the truck as you go.

4. The MultiPro Tailgate System

This configurable tailgate system is something buyers are digging. It was introduced back in 2019, and this system has six different functions. It has the traditional up/down opening, a secondary cutout piece that extends, and a multi-function inner gate. It is a cool concept that makes it easier for drivers to load and unload cargo.

5. Superior Steering

Steering is another area where the Sierra 3500HD shines. The steering is well-weighted and feels nimbler than some of its top rivals despite being kind of vague at higher speeds. For a heavy duty truck, the steering feels secure, agile, and responsive - and that is due in large part to its independent front suspension.

6. The Denali Trim Level

The Denali trim level definitely looks cool, and it has a lot of bells and whistles for those who want them. The Bose premium sound system is a huge selling point for it since this gives music lovers a concert-like listening experience. You also get nifty features like wireless smartphone charging, built-in navigation, an 8-inch driver information display, front and rear parking sensors, and the Driver Alert bundle full of advanced driver aids.

7. The AT4

If you plan on doing a lot of off-roading, then you might be more interested in the AT4. This trim level comes with mud-oriented tires (which are all new for the model year), standard 4WD, skid plates, an off-road tuned suspension, and a locking rear differential. Off-road drive mode, hill descent control, and hill start assist enhance the vehicle's stability and traction control. Also, you get the head-up display as a standard feature.

8. The SLT Convenience Package

If you get the SLT trim level, we definitely recommend checking out the SLT Convenience Package. This package consists of remote keyless entry, LED cargo box lighting, and a remote locking tailgate, just to name a few features. You also get upgraded to some comfy bucket seats.

9. Standard Technology on the Base Sierra Work Truck

Work trucks do not normally come with much on them, but the base Sierra 3500HD work truck actually has some fun features. Aside from LED headlights and chrome bumpers, you get tech features like Bluetooth connectivity, a 7-inch infotainment display, and smartphone app integration with Apple CarPlay and Android Auto.

10. Dual-automatic Climate Control

Having the dual-zone automatic climate control system come standard on the SLT and above feels fantastic. The system runs well and gets the truck heated up or cooled down as needed, equally tending to both rows of seats. Air flows evenly throughout, and rear seat passengers won't need to complain about being too hot or too cold. Everyone will feel nice and cozy. The heated steering wheel and heated and ventilated front seats you can get add even more layers of comfort.

Reasons You May Not Like the 2021 GMC Sierra 3500HD – The Cons

1. Poor Fuel Economy

The gas-powered V8 engine gets especially poor fuel economy, and the diesel is just kind of average. The EPA does not test heavy-duty trucks like the 2021 GMC Sierra 3500HD, but real-world estimates let us know that this truck is sub par on fuel. The Denali diesel has been shown to get just 17 mpg on the highway. This pales in comparison to the Silverado 2500 and Ram 2500, which get somewhere around 19 mpg on the highway. And the gas-powered V8 seems to do even worse than the diesel.

2. A Boring Gas-powered V8

In addition to being thirsty for fuel, the gas-powered V8 is just boring. The acceleration is nothing to write home about, and the amount of torque (464 lb-ft) pales in comparison to the diesel's impressive 910 lb-ft. The gas V8 just kind of sputters along, never acting like it is too thrilled to be out on the road.

3. Soft Brakes

Regardless of which engine you get, you are going to have to deal with some squishy brakes, and nobody likes squishy brakes. They seem to lose firmness pretty quickly too. The more you press down on them as you drive, the softer they get. You have to apply a lot of pressure to get the vehicle to stop in a timely fashion, so you can imagine how much effort it takes to come to a panic stop.

4. The Over-the-top Front Grille

This is a silly little gripe, but we think the front grille looks a bit excessive. There is a lot aesthetically going on, as if GMC is trying to do too many things at once to make the grille look cool. It just doesn't; it instead ends up being an eyesore.

How It Stacks Up to the Competition:

2021 GMC Sierra 3500HD vs. 2021 Ford F-350 Super Duty

Much like the 2021 GMC Sierra 3500HD, the F-350 Super Duty comes with a high-powered diesel engine option and immense towing and hauling capabilities. The Ford is also pretty efficient given its lightweight aluminum body design. You also get a bunch of cab configurations to choose from that are both spacious and practical. The one downside to this truck is that it gets pricier as you add on options.

2021 GMC Sierra 3500HD vs. 2021 Ram 3500

The 2021 Ram 3500 might have a busier ride quality than the Sierra 3500HD, but it gets quite a few things right. The diesel engine has a massive towing capacity, and the cabin is remarkably comfortable for a truck its size. On top of that, the multiple camera views you get of the trailer can really come in handy.


The 2021 GMC Sierra 3500HD is a heavy-duty pick-up truck that has wormed its way into the top four picks for its segment. With 2020's changes, the Sierra has managed to make itself a powerful contender with a fantastic diesel engine option that gives you more than enough torque. And you definitely will not be left wanting for towing and hauling capabilities.

Previous GMC Sierra 3500HD Buying Guides:

Why buy a 2020 GMC Sierra 3500HD? w/ pros vs cons