The GMC Sierra Heavy Duty underwent a complete overhaul (redesign and re-engineering) for the 2020 model year. As such, the model has received some minor changes and updates for 2021, which represents the second production year for the fourth-generation Sierra HD.
| Assembly Location | GM Flint Assembly in Flint, Michigan, USA and GM Fort Wayne Assembly in Fort Wayne, Indiana, USA | |
| Body Style(s) | Heavy-Duty Pickup Truck | |
| Layout | Front-Engined, Longitudinal | |
| Engine(s) | 6.6L L8T V8, 6.6L Duramax L5P V8 (Diesel) | |
| Transmission(s) | 6-Speed Auto, 10-Speed Auto, Allison 10-Speed Auto | |
| Drive Wheels | Rear-Wheel-Drive, Four-Wheel-Drive | |
| Availability | U.S.A., Canada, Mexico | |
| Predecessor | 2020 GMC Sierra HD | |
| Successor | 2022 GMC Sierra HD | |
Changes, Updates, New Features
Exterior
- Deletion of two exterior color options
- Addition of three exterior color options
- Deletion of 18-inch (45.7 cm) 6-spoke machined aluminum extended wheels with high gloss Black accents
- Addition of AT4 high clearance step (LPO-level item)
- Addition of power-retractable Assist steps with stainless steel accents
- Includes LED lights
- Addition of new, high gloss Black mirror caps for AT4 models
- Addition of LT275/70R18, mud-terrain, blackwall tires (QG3)
- For 2500HD models only, not available for 3500HD models
- Addition of 18-inch (45.7 cm) machined aluminum wheel with Dark Grey metallic accents (PXD)
- Addition of 20-inch (50.8 cm) high gloss Black painted aluminum wheels (RTJ)
- Addition of Bedside Storage, right hand and left hand side
- Addition of Tie-Downs option – includes 4
- Addition of 20-inch Transit wheels for 20-inch (LPO-level wheels)
- Addition of 20-inch machined aluminum wheel wheels with new finish and bright Silver accents
- Addition of 20-inch wheels with new finish, machined aluminum with high gloss Black accents
Interior
- Deletion of front 40/20/40 split-bench seat
- Deletion of single USB Port
- Addition of Premium floor liners with removable carpet inserts
- Front and rear
- Addition of inside rearview auto dimming mirror with partial video display
- Addition of Bed View Camera in the CHMSL to show a view of the cargo bed
- Display located in rearview mirror
- Front 40/20/40 split-bench seat with upper covered armrest storage is now standard on base (1SA) Sierra HD models
- SiriusXM is now standard on SLE models and available on base models
Mechanical
- Gasoline engine options are now E85 FlexFuel capable
- Standard tailgate is now available on SLE models
- Remains standard on base models, and is no longer available for SLT, AT4, or Denali models
- Deletion of manual tailgate function with lift assist
- GMC MultiPro Tailgate is now standard on SLE models
- For the 2020 models, SLE models came standard with
- Gooseneck / 5th Wheel Package is not available on Denali you now order the Gooseneck / 5th Wheel Prep Package free flow option
- Denali models only
- ProGrade Trailering System no longer includes Sirius X, EZ Lift, or power lock and release tailgate
Packaging
- Addition of the AT4 Premium Plus Package
- Addition of Denali Black Diamond Edition
- Addition of the X31 Off-Road and Protection Package
- Addition of 1SA Safety Confidence Package
- Technology Package  no longer includes Bed View Camera or HD Surround Vision
- New RPO code designation for SLT Premium Plus Package
- New RPO code designation for Texas Edition SLT Premium Plus Package
- SLE Convenience Package no longer includes EZ Lift power lock and release tailgate
- New SLT Preferred Package contents
- New AT4 Preferred Package contents
See detailed 2021 GMC Sierra HD changes, updates and new features here: 2021 GMC Sierra HD change log.
The updates and changes described here are specific to the U.S. market and may differ for other markets.
Body Styles
The 2021 Sierra HD is available as a 2500 or 3500 heavy-duty full-size pickup truck model with several cab and box configurations:
2500HD
- Regular Cab, Long Bed
- Double Cab, Standard Bed
- Double Cab, Long Bed
- Crew Cab, Standard Bed
- Crew Cab, Long Bed
3500HD
- Regular Cab, Long Bed
- Double Cab, Long Bed
- Crew Cab, Standard Bed
- Crew Cab, Long Bed
Models & Trims
The 2021 GMC Sierra HD is offered as a retail or fleet model, with the Sierra (1SA) being the base model.
2021 Sierra HD Retail & Fleet Models:
2500HD
- Standard Bed Crew Cab
- 2WD (TC20743)
- 4WD (TK20743)
- Long Bed Crew Cab
- 2WD (TC20943)
- 4WD (TK20943)
- Standard Bed Double Cab
- 2WD (TC20753)
- 4WD (TK20753)
- Long Bed Double Cab
- 2WD (TC20953)
- 4WD (TK20953)
- Long Bed Regular Cab
- 2WD (TC20903)
- 4WD (TK20903)
3500HD
- Standard Bed Crew Cab with Single Rear Wheel
- 2WD (TC30743)
- 4WD (TK30743)
- Long Bed Crew Cab with Single or Dual Rear Wheel
- 2WD (TC30943)
- 4WD (TK30943)
- Long Bed Double Cab with Single or Dual Rear Wheel
- 2WD (TC30953)
- 4WD (TK30953)
- Long Bed Regular Cab with Single or Dual Rear Wheel
- 2WD (TC30903)
- 4WD (TK30903)
2021 Sierra HD Retail & Fleet Trims:
2500HD
- Sierra base
- SLE
- SLT
- AT4
- Denali
3500HD
- Sierra base
- SLE
- SLT
- AT4
- Denali
Powertrain
The 2021 GMC Sierra HD is offered with the following engine and transmission choices:
| Engine | Fuel | Aspiration | Transmission | Horsepower @ RPM | Torque @ RPM | Axle |
|---|---|---|---|---|---|---|
| 6.6L L8T V8 | Gasoline | Naturally Aspirated | 6-Speed Automatic (MYD) | 401 @ 5200 | 464 @ 4000 | 3.73 |
| 6.6L Duramax L5P V8 | Diesel | Turbocharged | 10-Speed Automatic (MGM, MGU) | 445 @ 2800 | 910 @ 1600 | 3.42 |
Platform
The 2021 Sierra Heavy Duty rides on a more capable version of the GM T1 platform that also underpins the 2020 Sierra 1500, 2020 Yukon, as well as other full-size GM trucks and SUVs.
Production
The 2021 Sierra HD was assembled at the GM Flint Assembly Plant in Flint, Michigan, USA.
Availability
2021 Sierra HD units should reach dealer lots by the end of the third quarter of 2020.
Beyond 2021
We expect the fourth-generation Sierra HD to remain in production thru the 2026 model year.
An all-new, next GMC Sierra HD will launch after the 2026 model year.
Sales
See GMC Sierra sales numbers for all markets, including the United States, Canada, Mexico, and China.
Notes:
- GMC Sierra sales are comprised of all Sierra variants, including light duty (1500), heavy duty (2500, 3500), and medium duty models (4500, 5500, 6500).
- Information for market (country) specified.
- Sales information compiled from various sources by GM Authority and Motrolix.
Gallery
Discussion
Discuss the 2021 GMC Sierra HD in our GMC forum.
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