“That it is the best riding truck and has the most power I've ever owned. Only disappointment is the adaptive cruise control and lane holding do not actually function as such, Indicator lights and a vibrating seat does not qualify as such!!”
2020 GMC Sierra 3500: What's New, Specs & Features
Last updated August 4, 2026
The 2020 GMC Sierra 3500 is an all-new fourth-generation truck, not a minor update. Its biggest change is a complete heavy-duty redesign built around a stronger new platform.
About the 2020 GMC Sierra 3500
4th generation, first year (all-new for 2020)
GMC positions the Sierra HD as a professional-grade heavy-duty truck that does serious towing and hauling without feeling stripped down or purely work-focused. Its core appeal is big capability paired with smarter trailer technology, a roomier cab, and more upscale trim personalities than many rivals. The lineup especially leans into premium comfort and distinct personalities through SLT, AT4 and Denali, rather than selling only on raw tow numbers.
The 2020 lineup spans work-focused trucks, more polished towing trims and the leather-lined Denali. SLT blends leather seating with the MultiPro tailgate and ProGrade trailering system, while the new AT4 adds off-road suspension, skid plates and an automatic locking rear axle. Denali emphasizes comfort and technology with navigation, Bose audio, heated and ventilated leather seats and a broad driver-assist suite.
What changed, by category
Structural
The Sierra 3500 moved to a new heavy-duty platform with a stronger fully boxed frame, a larger cab and bed, and more passenger room. Towing and hauling capability increased substantially from the previous generation.
Powertrain
A new 6.6-liter gas V8 with direct fuel injection replaced the old 6.0-liter gas engine. The Duramax diesel was paired with a new Allison 10-speed automatic. Flexible-fuel versions were dropped across the returning trims, and natural-gas versions left the Base, SLE and SLT lineups.
Styling and trim lineup
The larger body arrived with the redesign, and the first dedicated Sierra HD AT4 joined the range. AT4 brought red recovery hooks, a trim-specific cabin, off-road suspension, skid plates and an automatic locking rear axle.
Tech
GMC added trailering technology centered on the ProGrade Trailering System. SLT gained a standard MultiPro tailgate, a high-definition rear camera and a standard heated steering wheel; satellite radio and the touchscreen monitor changed from standard to optional on that trim.
Safety
Denali expanded its standard driver-assist equipment, including automatic emergency braking, lane-departure warning, blind-zone alert and rear cross-traffic alert.
2020 GMC Sierra 3500 specs and features by trim
| Feature | |||||
|---|---|---|---|---|---|
| Engine | V8, 6.6 Liter / V8, Turbo Diesel, 6.6 Liter | V8, 6.6 Liter / V8, Turbo Diesel, 6.6 Liter | V8, 6.6 Liter / V8, Turbo Diesel, 6.6 Liter | V8, 6.6 Liter / V8, Turbo Diesel, 6.6 Liter | V8, 6.6 Liter / V8, Turbo Diesel, 6.6 Liter |
| Transmission | Automatic, 6-Spd HD w/Overdrive | Automatic, 10-Spd Allison / Automatic, 6-Spd HD | Automatic, 10-Spd Allison | Automatic, 6-Spd HD w/Overdrive / Automatic, 6-Spd HD | Automatic, 6-Spd HD w/Overdrive |
| Drivetrain | 4WD | 4WD | 4WD | 4WD | 4WD |
| Fuel Type | Gas / Diesel | Gas / Diesel | Gas / Diesel | Gas / Diesel | Gas / Diesel |
| Horsepower | 445 hp | 401–445 hp | 445 hp | 401–445 hp | 445 hp |
| Torque | 910 lb-ft | 464–910 lb-ft | 910 lb-ft | 464–910 lb-ft | 910 lb-ft |
| Max Towing | 14500 lb | 14500–16300 lb | 14500–16300 lb | 14500–16300 lb | 14500 lb |
| Rear Legroom | 43.4 in | 35.2–43.4 in | 43.4 in | 35.2–43.4 in | 43.4 in |
| Seats | 3–6 | 6 | 3–6 | 5 | |
| Doors | 4 | 2–4 | 4 | 2–4 | 4 |
| Alarm System | |||||
| Automatic Emergency Braking | |||||
| Automatic High Beams | |||||
| Blindspot Sensors | |||||
| Cruise Control | |||||
| Hill Descent Control | |||||
| Lane Departure Warning | |||||
| Park Assist | |||||
| Rear View Camera | |||||
| Alloy Wheels | |||||
| Fog Lights | |||||
| HID Headlights | |||||
| Heated Mirrors | |||||
| LED Headlights | |||||
| Memory Exterior Mirrors | |||||
| Power Moonroof | |||||
| Power Mirrors | |||||
| Privacy Glass | |||||
| Side Steps | |||||
| Tow Hooks | |||||
| Head-Up Display | |||||
| Navigation System | |||||
| Premium Audio | |||||
| Rear DVD Entertainment System | |||||
| SD Card Slot | |||||
| Smartphone Interface | |||||
| Subwoofer | |||||
| Touch Screen Monitor | |||||
| Auto-Dimming Interior Mirror | |||||
| Dual Power Front Seats | |||||
| Dual-Zone Climate Control | |||||
| Heated Front Seats | |||||
| Heated Rear Seats | |||||
| Heated Steering Wheel | |||||
| Integrated Garage Door Opener | |||||
| Leather Seats | |||||
| Leather-Wrapped Steering Wheel | |||||
| Memory Driver's Seat | |||||
| Power Adjustable Pedals | |||||
| Power Driver Seat | |||||
| Remote Start | |||||
| Remote Keyless Entry | |||||
| Tilt Wheel | |||||
| Tilt/Telescoping Steering Wheel | |||||
| Ventilated Front Seats | |||||
Frequently asked questions
Was the 2020 GMC Sierra 3500 fully redesigned?
Yes. The 2020 GMC Sierra 3500 began its fourth generation with a new heavy-duty platform, stronger fully boxed frame, larger cab and bed, and substantially greater towing and hauling capability.
What powertrain changes did the 2020 GMC Sierra 3500 receive?
The main powertrain change was a new 6.6-liter gas V8 replacing the previous 6.0-liter gas engine. The Duramax diesel was also paired with a new Allison 10-speed automatic, while the prior flexible-fuel and natural-gas offerings were dropped from applicable trims.
Was the GMC Sierra 3500 AT4 new for 2020?
Yes. The 2020 model year introduced the first dedicated Sierra HD AT4, with four-wheel drive, off-road suspension, Rancho shocks, skid plates, an automatic locking rear axle and an AT4-specific cabin.
Did towing capability improve on the 2020 GMC Sierra 3500?
Yes. Towing capability increased substantially for 2020, supported by the stronger frame, new powertrain combinations and new ProGrade trailering technology.
Is the 2020 GMC Sierra 3500 meaningfully different from the 2019 model?
Yes. The 2020 truck is a full redesign with a stronger frame, larger cab and bed, new 6.6-liter gas V8, 10-speed automatic for the diesel, higher towing capability and newer trailering technology. It is a much broader update than a routine equipment change.
2020 GMC Sierra 3500 Reviews
What owners are saying about the 2020 GMC Sierra 3500.
4.3
2020 GMC Sierra 3500
(286 reviews)
“Definitely worth getting. All bells and whistles. Great cargo space and spacious interior.”
“The power coming from the engine and the smoothness of the transmission. Best looking truck on the road.”