2020 GMC Sierra 3500HD

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2020 GMC Sierra 3500HD Review: Heavy-Duty Mega Hauler

When it comes to the heaviest haulers in the full-size truck market in the US, few do it better than the 2020 GMC Sierra 3500HD heavy-duty truck. It is made to haul enormous loads and carry massive payloads, as are rivals like the Chevrolet Silverado 3500HD and the Ford F-350 and F-450 Super Duty. After doing duty in the USA since the nameplate was first introduced in 1988, the Sierra has been redesigned for 2020, with the fifth-generation model sporting an all-new design and improved fuel economy and safety. In terms of its drivetrain, the Sierra 3500HD delivers with a 10-speed automatic transmission and 6.6-liter gasoline V8 with 401 horsepower or an available turbocharged 6.6-liter V8 diesel with 445 hp, so it can do all the heavy lifting demanding owners require. However, competition is strong in this class and its rivals have not been napping, offering mostly better interiors than the GMC. Still, GMC hopes to have a leg up on them with features like the world-first six-function MultiPro tailgate.

Read in this review:

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2020 GMC Sierra 3500HD Changes: What’s The Difference vs The 2019 GMC Sierra 3500HD?

With the end of the decade comes an all-new GMC Sierra, much to the delight of truck lovers across America. The 2020 Sierra 3500HD is taller and longer in design and gets new signature lighting, which consists of a set of 'light blades' - LED daytime running lamps. On the inside, the truck's new interior boasts best-in-class front head- and legroom in Crew Cab models. The hardcore Sierra AT4 Heavy Duty gets some cutting-edge technologies that include robust off-road suspension, Rancho Shocks, skid plates, and an Eaton locking rear differential. An all-new 6.6-liter V8 generating 401 hp and 464 lb-ft of torque makes its way into the range and is paired to a 6-speed automatic transmission and 2-wheel- or 4-wheel drive.

Pros and Cons

  • Gas and diesel V8 engines both have plenty of power
  • Impressive hauling performance and towing capacity
  • Advanced 10-speed automatic transmission
  • MultiPro tailgate is revolutionary
  • Substandard cabin
  • Appearance divides opinions
  • Brakes not class-leading

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2020 GMC Sierra 3500HD Trims and Prices

See trim levels and configurations:

Trim Engine Transmission Drivetrain Price (MSRP)
6.6L V8 Gas
6-Speed Automatic
Rear-Wheel Drive
Four-Wheel Drive
6.6L V8 Gas
6-Speed Automatic
Rear-Wheel Drive
Four-Wheel Drive
6.6L V8 Gas
6-Speed Automatic
Rear-Wheel Drive
Four-Wheel Drive
6.6L V8 Gas
6-Speed Automatic
Four-Wheel Drive
6.6L V8 Gas
6-Speed Automatic
Four-Wheel Drive

Sierra 3500HD Exterior

2020 GMC Sierra 3500HD Front View Driving GMC
2020 GMC Sierra 3500HD Side View Driving GMC
2020 GMC Sierra 3500HD Frontal Aspect GMC
See All 2020 GMC Sierra 3500HD Exterior Photos


  • Length 250.1 in
  • Wheelbase 158.9 in
  • Height 80.9 in
  • Max Width 81.9 in

Exterior Colors

Sierra 3500HD Performance

2020 GMC Sierra 3500HD Side Angle Driving GMC
2020 GMC Sierra 3500HD Forward View GMC
2020 GMC Sierra 3500HD Wheel GMC

Engine and Transmission

This year, the new-for-2020 6.6-liter gas V8 generates 401 hp and 462 lb-ft of torque, paired to a 6-speed automatic transmission. The sole diesel option is a 6.6-liter turbocharged V8 with 445 hp and 910 lb-ft, mated to an Allison 10-speed automatic transmission. 2-wheel-drive and 4-wheel-drive drivetrains are available, as well as single and dual rear wheels. The Sierra 3500HD has a towing capacity of up to 35,500 pounds when equipped with the diesel engine.

  • Engines
    6.6L Turbo V8 Diesel, 6.6L V8 Gas
  • Transmissions
    10-Speed Automatic, 6-Speed Automatic
  • Drivetrains
    4X4, RWD

Sierra 3500HD Gas Mileage

  • Fuel Tank Capacity
    36.0 Gallons
* 2020 GMC Sierra 3500HD 2WD Crew Cab 159"

Sierra 3500HD Interior

2020 GMC Sierra 3500HD Central Console GMC
2020 GMC Sierra 3500HD Infotainment System GMC
2020 GMC Sierra 3500HD Interior Wooden Trim GMC
See All 2020 GMC Sierra 3500HD Interior Photos

Seating and Interior Space

  • Seating capacity
  • Front Leg Room 44.5 in
  • Front Head Room 43.0 in
  • Rear Leg Room 43.4 in
  • Rear Head Room 40.1 in

Sierra 3500HD Trunk and Cargo Space

2020 GMC Sierra 3500HD Dashboard GMC
2020 GMC Sierra 3500HD Cargo Room GMC
2020 GMC Sierra 3500HD Trunk Space GMC

Sierra 3500HD Safety and Reliability


  • Basic:
    3 Years \ 36,000 Miles
  • Drivetrain:
    5 Years \ 60,000 Miles
  • Drivetrain Note:
    HD Duramax Diesel: 5 Years \ 100,000 Miles; Qualified Fleet Purchases: 5 Years
  • Rust-Through:
    6 Years \ 100,000 Miles
  • Corrosion:
    3 Years \ 36,000 Miles
  • Roadside Assistance:
    5 Years \ 60,000 Miles
  • Roadside Assistance Note:
    HD Duramax Diesel: 5 Years \ 100,000 Miles; Qualified Fleet Purchases: 5 Years
  • Maintenance Note:
    1 Year \ 1 Visit

US NHTSA Crash Test Result

NHTSA safety ratings are not available at this time.

Verdict: Is the 2020 GMC Sierra 3500HD A Good Truck?

Not everybody loves the way the new 2020 GMC Sierra 3500HD pickup truck looks, but ability and reliability are more important in this class than trivialities such as style and here, this heavy hauler delivers, particularly in diesel guise. The new gasoline V8 engine, impressive as it is, can wilt under the heaviest loads at times, whereas the formidable turbo-diesel engine and its great new 10-speed Allison transmission always seem to have an answer. Sadly, the vehicle's interior is less hit and more miss, falling short in terms of design and quality compared to products from Ford and Ram. If you don't mind the subpar cabin - and working hard is all you want to do - the Sierra will certainly meet your expectations, especially the diesel with its mammoth torque and superior gas mileage.

What GMC Sierra 3500HD Model Should I Buy?

You likely wouldn't be reading a review of the 2020 GMC Sierra 3500 HD if you weren't in need of something that can haul big loads. That's why we'd recommend looking at the diesel engine right of the bat to unlock the highest available towing capacity. After that, it really is up to you to choose whether you want a 2-door or 4-door cab, what load bed length you require, and which specification level will strike the best balance of heavy-duty workhorse and comfortable commuter. Given GMCs are technically supposed to be a little more luxurious and are bought by a slightly different clientele to their Chevrolet counterparts, you'll likely want to look at either an SLT, off-road-biased AT4, or the ultra-luxe Denali. However, for the latter, the price of the 2020 GMC Sierra 3500HD truck can easily surpass $70,000.

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