2021 GMC Sierra Heavy Duty in Alliston, ON

GMC Sierra 2500HD & 3500HD at Ernie Dean

The 2021 GMC Sierra Heavy Duty is the best value truck you can get here in Ontario, a hardworking pickup that doesn’t sacrifice on style, luxury or tech. Across the base, SLE, SLT, AT4 and Denali trim levels you’ll be met with supreme towing ability, generous cargo bed space, convenient comfort features, advanced safety and so much more. Whether you’re on the job site, off-road, or just driving through a city, the 2021 GMC Sierra 2500HD & 3500HD provides the benchmark of what all heavy duty pickup trucks strive to be. Learn more about this Sierra HD here at Ernie Dean, and shop for one for sale at our GM dealership!

View our Heavy Duty towing guide here

Browse our full lineup of GMC pickups here: 2021 GMC Sierra 1500, 2021 GMC Canyon

Exterior Design

Heavy Duty Top Features

The Sierra 2500 & 3500 are large and in charge, presenting a huge exterior that is not only ready to accomplish any job thanks to its heft, but also because of its many fine-detail highlights that underline its size with top-level features.

Trailering Mirrors: These power-fold mirrors will manually extend and retract, complete with LED guidance lights to improve visibility.

Side Bed Step: This complementary piece to the CornerStep allows you to easily grab your gear from the bed.

Dual-Path Air Induction System: On the Duramax Turbo-Diesel engine comes this Dual Path Air Induction system, taking in cool air through the hood scoop and front grille to cool the inside temperature and increase performance.

Lighting: Featured is LED headlights, LED tail lights, LED daytime running lamps, available LED fog lamps, available LED cargo bed lights and more.

AT4 Highlights

Want a heavy duty pickup that’s specifically designed to tackle your off-road needs, and does so in an athletic style? The AT4 pairs these both together to deliver a truly modern HD Sierra option. The AT4 is highlighted by many features, including:

  • Exclusive style features
  • Vertical red recovery hooks
  • High clearance step

Denali Premium Highlights

For the best of the best on the Sierra 2500HD & 3500HD, acquaint yourself with the top-level Denali trim, featuring the ultimate in premium touches. These are all highlighted by the following:

  • Signature Denali grille
  • Chrome 6-inch assist steps
  • Chrome vertical front recovery hooks
  • Chrome handles and mirror caps
  • Dual-Path Air Induction system
  • 20-inch Multi-Dimensional polished aluminum wheels
  • MultiPro tailgate

Cargo Beds & Tailgate

The heavy-duty cargo bed comes with best-in-class volume, with standard and long bed options on a roll-formed high-strength steel floor. 12 cargo tie-downs will keep your cargo secure, while available LED lighting and a spray-on bedliner provide further utility to get the most out of your bed. The unique MultiPro tailgate provides 6 different ways to open, which are:

  • Primary Gate
  • Primary Gate Load Stop
  • Easy Access
  • Full-Width Step
  • Inner Gate Load Stop
  • Inner Gate with Work Surface

Exterior Dimensions

Dimensions:Sierra HD Denali (Crew Cab, Standard Bed)Sierra HD Denali (Crew Cab, Long Bed)
Length (mm/in)6,352 / 250.086,759 / 266.09
Width (without mirrors) (mm/in)2,079 / 81.852,079 / 81.85
Height (mm/in)2,027 / 79.822,023 / 79.65
Wheelbase (mm/in)4,037 / 158.944,369 / 172.00
Cargo Box Length (on floor) (mm/in)2,088 / 82.2024,96 / 98.27
Cargo Box Width (on floor) (mm/in)1,814 / 71.401,814 / 71.40
Ground Clearance (mm/in)257 / 10.12256 / 10.08
Cargo Volume (L)1,9682,364

Interior Design

Interior Comfort Highlights

Every piece of the interior inside the Sierra HD was designed with the best intentions of the driver and passengers in mind. Both elegant and spacious, the cabin is designed to meet those inside with high quality materials and a design that is supremely intuitive. Available is a leather-wrapped heated steering wheel, heated/ventilated front seats and dual-zone climate control to regulate temperature.

AT4 Adventure-Ready Interior

The beauty of the AT4 is that it expertly balances perfectly styled interior touches with purposeful features.

  • Heated/ventilated front leather seat surfaces
  • Heated leather-wrapped steering wheel
  • Jet Black & Kalahari interior
  • Front & rear floor liners (featuring removable carpet inserts)
  • AT4 embroidered logos
  • Rear seatback, plus under-seat storage
  • HVAC system, with dual-zone climate control

Premium Denali Interior

The ultimate in premium features of the Denali’s exterior is continued on the inside with its elegant touches throughout.

  • Jet Black & Denali Dark Walnut/Dark Ash Grey interiors
  • Open-Pore Ash Wood, brushed aluminum trim, chrome accents
  • Heated rear outboard seats
  • Leather seat surfaces with heated/ventilated bucket seats


It’s not just the generous cargo bed that’s available to take on all of the gear you desire to haul and store onboard, the interior includes a variety of smart storage options, too. Rear seat storage features available seatback storage that safely stays secure. Crew Cab models feature a rear-fold split bench with handy under-seat storage opportunities. Up front is the generous centre controls, including a lockable vault for your valuables.

Dimensions:Sierra Heavy Duty Denali Crew Cab
Front Headroom (mm/in)1,093 / 43.03
Rear Headroom (mm/in)1,013 / 39.88
Front Legroom (mm/in) 1,131 / 44.53
Rear Legroom (mm/in)1,102 / 43.40
Front Shoulder Room (mm/in)1,677 / 66.02
Front Shoulder Room (mm/in)1,659 / 65.30
Front Hip Room (mm/in)1,554 / 61.18
Rear Hip Room (mm/in)1,530 / 60.24
Passenger Capacity5

Performance & Capability

Engine & Transmission Options

The Sierra HD comes fit with your choice of two engines, either the 6.6L V8 gas engine as standard or the available 6.6L Duramax Turbo-Diesel V8 engine (with the Allison 10-speed automatic transmission). These advanced engines combine for brawny power that delivers a stable and powerful drive, and a confident trailering experience when towing.

HD Capability

This heavy duty pickup delivers high-powered engine performance thanks to some of its top AT4 and Denali features. Their independent front suspensions equal exceptional wheel alignment, a comfortable ride and easy turnability. Payload and ride quality is managed in equal measure thanks to the two-stage, semi-elliptic multi-leaf rear springs. To keep the truck at the perfect temperature with the Duramax engine is a big 28-inch cooling fan is put to work, with the Dual Path Air Induction system drawing in cool air. A Diesel After-Run also helps to cool the engine down after heavy activity.

Stop & Go Tech

Stop & Go technology mixes and matches performance capability with advanced tech that provide supremely effective whether you’re stopped or on the go. These many features include:

  • Auto Electric Parking Brake Assist
  • Park Grade Hold Assist
  • Digital Variable Steering Assist
  • 2-Speed Autotrac Transfer Case
  • Traction Select System (with Tow/Haul and Off-Road Mode)
Specifications:Gas V8Turbocharged Diesel V8
Transmission6-speed automatic (heavy duty), Allison 10-speed automatic6-speed automatic (heavy duty), Allison 10-speed automatic
Torque (lb-ft)464910


ProGrade Trailering System

Get the most out of your trailering experience with the Sierra HD and its ProGrade Trailering system. This intelligent tech makes everything from hitching to towing a breeze, providing an easy-to-use command centre to stay up-to-date with the entire system. Features include an in-vehicle trailering app, myGMC mobile app, smart trailer integration and new for 2021 is the available jack-knife alert.

Camera & View Systems

Get the best perspective in and around the Sierra Heavy Duty thanks to the variety of camera and view features found onboard. Up to 15 available camera views are available, through systems and views like HD Surround Vision, the Rear Camera Mirror and Bed View Camera. Also, rely on the 15-inch head-up display to keep tabs on important info while keeping your eyes glued to the road ahead.


Your pickup and smartphone can simply connect together to make a whole thanks to the connective options of Apple CarPlay and Android Auto to make use of your favourite device’s apps. Amazon Alexa is built-in, providing another destination for navigation, entertainment, calls and much more.


Safety & Driver Assistance Tech

Be better prepared and aware of all that’s around you on each and every drive thanks to the safety and driver assistance technology found aboard the Sierra HD. These intelligent features provide helpful aid making sure your next ride is as safe as possible. Highlighted features include Lane Departure Warning, to ensure you stay in your lane with alerts if you drift, and Front & Rear Park Assist, to detect close-by objects when you’re parking.

Advanced Safety

The Sierra HD never settles for less when it comes to hardworking performance, and doesn’t do so either when it comes to advanced safety features. Some of these top-level systems include:

  • Automatic Emergency Braking
  • Following Distance Indicator
  • Forward Collision Alert
  • Lane Change Alert (with Side Blind Zone Alert)
  • Rear Cross Traffic Alert

What’s New From the 2020 GMC Sierra Heavy Duty?

Trailer assistance features act as some of the big changes on the 2021 GMC Sierra HD! New is jack-knife alert, bed view (with zoom hitch guidance), rear trailer view and forward and reverse rear side view bias, adding on even more helpful tech to put you in further control of every towing job. A Denali Black Diamond Edition has been added, providing a premium look with black elements for dramatic styling. This all comes after the redesign from last year, keeping the advanced styling the same and focusing on adding new towing aides along with package options.

2021 Sierra Heavy Duty Trims

*These prices are reflective of the 4WD Crew Cab Standard Bed models, and are subject to change

Front side view of GMC Sierra Heavy Duty


Starting at $54,848*

Highlighted features:

  • 16,329 kg max towing
  • ProGrade Trailering System
  • Advanced camera views
  • MultiPro tailgate
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Front side view of GMC Sierra Heavy Duty SLE


Starting at $60,148*

Highlighted features:

  • 16,329 kg max towing
  • ProGrade Trailering System
  • Advanced camera views
  • MultiPro tailgate
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Front side view of GMC Sierra Heavy Duty SLT


Starting at $69,048*

Highlighted features:

  • 16,329 kg max towing
  • ProGrade Trailering System
  • Advanced camera views
  • MultiPro tailgate
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Front side view of GMC Sierra Heavy Duty AT4


Starting at $71,348*

Highlighted features:

  • Off-road suspension
  • Exclusive black chrome exterior accents
  • Allison 10-speed automatic transmission
  • Exclusive athletic interior
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Front side view of GMC Sierra Heavy Duty Denali


Starting at $78,248*

Highlighted features:

  • Signature Denali grille
  • Open-pore ash wood, brushed aluminum trim
  • Allison 10-speed automatic transmission
  • Head-up display
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Ernie Dean is your one-stop destination for everything you want to know about trucks! From GMC to Chevrolet, from light-duty to heavy-duty, if it’s a pickup we have what you need. Whether that’s shopping for a new or used model, finding parts, getting service, or if you just want to chat, we here at Truckville will be happy to help you out! Contact us, today, with any questions, or fill out the form below to book a test drive!

Interested in more pickup truck models? Explore these options:

2021 Chevrolet Silverado 1500

2021 Chevrolet Colorado

2021 Chevrolet Silverado Heavy Duty

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