The 2021 GMC Sierra 3500HD is a powerful workhorse truck. That is usually all there is to trucks of this size and weight class. The Sierra 3500HD, however, manages to be something more. It's also a comfortable and luxurious daily driver. GMC has even provided the Sierra 3500HD with an attractive and stylish exterior design.
The Sierra 3500HD is the largest truck in GMC's lineup. The letters HD stand for heavy duty to signify the high payload and towing capacities of this vehicle. It's quite the off-road performer too, with 4X4 variations for most of the trim levels. This truck comes in five different trim levels, numerous configurations and one special edition for 2021.
GMC offers this truck in Regular, Double and Crew Cab body styles. Buyers will also have the choice of a 6.75-foot or 8-foot bed length. There are a couple of different powertrain options as well, including a powerful V8 diesel engine. We will take a close look at every trim level and what each has to offer.
Compare the 2021 GMC Sierra 3500HD Base vs SLE - What is the Difference?
The Base trim level can be had in the Regular, Double and Crew Cab configurations. The Regular and Double Cabs come with a long bed. The Crew Cab has either a long bed or the standard length of 6.75 feet. A Regular Cab is a two-door model while the Double adds a small door and a larger backseat area. The Crew Cab has four full-sized doors with plenty of room for the rear passengers.
This trim can also be purchased with two-wheel drive or four-wheel drive. It comes with either single rear wheels or dual rear wheels. For anyone who has never had a truck in this weight class before, this means you can get a regular two-wheel setup in the back or double up on the number of wheels. This allows for a higher payload capacity.
The Base model comes stock with a 6.6-liter V8 gasoline engine. This engine has direct injection with variable valve timing. It produces around 401 horsepower with 464 pound-feet of torque. You also get a six-speed automatic transmission with this powertrain setup.
The base engine can be swapped out for the 6.6-liter Turbo-Diesel engine if you wish. That choice comes with an Allison 10-speed automatic transmission. A diesel-powered Crew Cab has a maximum payload capacity of 4,185 pounds. With dual rear wheels and the right equipment, it can tow up to 36,000 pounds.
On the outside of the Base trim, you get LED headlights, LED taillights and a set of 18-inch wheels with all-terrain tires. The exterior mirrors, door handles and belt-line moldings are all painted black. There are cargo lamps mounted to the cab and a total of 12 cargo tie-downs. The grille and both bumpers are covered in chrome.
This trim level comes with a standard tailgate. This still comes with GMC's EZ Lift system. The tailgate can be locked into place if needed. Every model gets solar-absorbing glass for all windows.
At this trim level, the interior offers four-way manual seats. This is a 40/20/40 split-bench setup. The instrument cluster features a 3.5-inch monochromatic Driver Information Center. You get a basic infotainment system and audio setup with a 7-inch touchscreen and six speakers.
Power windows and locks are standard here. The upholstery is vinyl for easy cleaning. The floor is made of a rubberized vinyl. There's a basic heater and A/C setup with Single-Zone Climate Control. The Base model has six airbags, a Rear-Vision Camera and a Tire-Pressure Monitoring System.
GMC has a system called Teen Driver. Every trim level of the 2021 GMC Sierra 3500HD gets this technology. It allows the truck owner to set parameters for younger, second drivers. It also gives you a report card to let you know how the driver is doing. All trims also have StabiliTrak which provides stability and traction control.
The SLE trim is the next level up. It comes with the same engine choices and optional transmission systems as before. It is available in all of the same body styles and configurations. On the outside, the first new addition is a set of 18-inch machined-aluminum wheels with glossy black accents.
The SLE swaps out a lot of the black trim on parts like the door handles for body-colored parts. The belt-line moldings now come in a steel color. This trim level adds on deep-tinted glass too. The tailgate with EZ lift adds on Lower Assist as well. All other exterior features remain the same as the Base model.
Moving on to the inside, the SLE gets a bigger driver-info display in the instrument cluster. The infotainment system gets some upgrades too. You can get a larger 8-inch touchscreen along with 4G WiFi Hotspot capability. GMC Connected Access and OnStar are available for this model. The steering wheel comes wrapped in leather at this trim level.
The rear area now gets rubberized vinyl floor mats. The upholstery is upgraded to fine cloth. Audio-system controls now come mounted on the steering wheel for easy, safer access. You also get some extra USB ports at this trim level for charging up your phones and other devices. The SLE also offers Keyless Entry.
The standard safety features are no different than the base model. There are some new optional add-ons though. There's an available Bed-View Camera so you can keep an eye on your cargo. The regular Rear-Vision Camera can be upgraded to high definition. You can get a Hitch Guidance with Hitch View and a Tire-Pressure Monitor for your trailer tires.
Compare the 2021 GMC Sierra 3500HD SLE vs SLT - What is the Difference?
The SLT trim is only available as a Crew Cab with either a standard or long bed length. It is also available in two-wheel drive and four-wheel drive variations. You can get one with single or double rear wheels as well. The SLT comes stock with the V8 gasoline engine. The diesel engine is still optional for this trim level.
The SLT offers GMC's MultiPro Tailgate. This setup gives you six different functions to make loading and unloading easier. There is a power lock and release with this tailgate. You also get some additional lighting in the hitch area.
Four-wheel drive versions of the SLT will have a 2-speed transfer case with push-button controls. This model also gets Digital Variable Steering Assist. This technology adjusts the steering dynamics for optimal performance under different driving conditions. The SLE has an optional Trailering Package while the SLT gets access to the Prograde Trailering Package with Hitch Guidance.
For the exterior, both models feature the same 18-inch aluminum wheels. These have a 6-spoke design and glossy-black accents. The cargo bed gets some addition LED lights on the SLT trim. On the inside of the SLT, the seats are upgraded to models with 10-way power adjustments and lumbar support.
The front bench seat gets an extra storage compartment underneath of it for this trim. There is now dual-zone climate control. The front seats now offer a heating feature. The safety features remain mostly the same. The Rear-View Camera gets upgraded to an HD model. Lane Departure Warning is optional for the first time at this trim level.
Compare the 2021 GMC Sierra 3500HD SLT vs AT4 Trim Level. - What is the Difference?
The AT4 trim level was built for optimal off-road performance. As such, it can only be purchased with 4X4 four-wheel drive. It is only available in the Crew Cab, but you can choose either a regular or long cargo bed. The AT4 is not available in a dual rear-wheel setup.
The main draw for the AT4 is the X31 Off-Road Package. This includes an upgraded off-road suspension, twin-tube Rancho shocks, skid plates and Hill Descent Control. There are also X31 Off-Road badges on the exterior to show off your truck's off-road capabilities. All of the safety features from the SLT trim make a return here.
On the inside, the AT4 gets all-weather floor liners with the AT4 logo. You get the top-tier infotainment system with Bluetooth connectivity and a WiFi Hotspot. There are extra USB ports here for even more charging stations and connectivity options. In addition to the front seats, the rear seats also now have the heating feature.
Compare the 2021 GMC Sierra 3500HD AT4 vs Denali Trim. - What is the Difference?
The AT4 is the off-road king of the 2021 GMC Sierra 3500HD lineup. The Denali is the luxury model of the bunch. It still offers the same amazing performance with the ability to tow or haul massive loads. This model, however, was also crafted with comfort and convenience in mind. It's an excellent vehicle for daily commutes and family hauling.
The Denali is only available in the four-door Crew Cab variation, as should be expected for a luxury truck. You can get a regular or extended cargo bed if needed. You can also get a Denali with the dual rear wheels if you should need the extra hauling capacity.
The AT4 and Denali both come equipped with the gasoline-powered V8. The Diesel engine is optional for both. Two nice additions to the Denali are the Driver Alert Packages. There are two of them added on here. This includes features such as Lane Change Alert with Side Blind Zone Alert and Rear Cross Traffic Alert.
Perimeter lighting is added at this level. You also get Front and Rear Park Assist. Forward Collision Alert, Automatic Emergency Braking and a Following Distance Indicator are all included here. For the exterior, the Denali gets plenty of chrome trim on the door handles, the grille and more.
The infotainment system for the Denali gets a navigation system to help you find your destination. The audio system gets upgraded to a Premium Bose Package with seven speakers and a Richbass woofer. An included Home Remote gives the driver access to garage doors and home security systems.
2021 GMC Sierra 3500HD Special Editions
In addition to the standard trim levels, there is also a special edition of the 3500HD Denali for 2021. This model is called the Denali Black Diamond Edition. This model comes in a single rear-wheel configuration with four-wheel drive. It comes equipped with a 6.6-liter Turbo-Diesel V8 and a 10-speed automatic transmission.
This special edition comes in a unique paint color that GMC calls Ebony Twilight Metallic. It has a blacked-out motif with a darkened grille, bumpers and exterior mirrors. The 20-inch aluminum wheels come in a special glossy-black paint scheme as well. Other than the cosmetic flourishes, this model is largely the same as a standard 3500HD Denali.
Some highlights here include a power sunroof, power-retractable steps and exterior lighting via some powerful LEDs. All-weather floor liners and removable carpets make cleaning out the truck a breeze. Also included is a premium audio system from KICKER.
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Which Trim to Choose?
There are a lot of choices to make when selecting the right 2021 GMC Sierra 3500HD for your specific needs. The bed length is completely subject to how much space you will need for hauling. Most drivers will be fine with a 4X2 model if they only plan to drive on paved roads, but a 4X4 model will have better handling during all weather conditions. Better handling and versatility make 4X4 models preferable in most cases.
Crew Cabs will be the most versatile option. They allow for more passenger space with easier access to the rear seats too. If you don't need the extra room for people, you can save some money by going with the Regular Cab. If you want a family hauler, go right for the top-tier Denali model. You'll get the best convenience features and the most comfortable interior.
If you want an off-road beast, the AT4 is your best bet. For most drivers who will use the 3500HD for both work and regular commutes, the SLT model will be the best bargain. You get an amazing set of features to make the interior a pleasant place to be. You also get excellent performance for just a small price increase over the Base and SLE trims.
• Compare the 2020 GMC Sierra 3500HD Trim Levels