The GMC Sierra 3500HD, specifically the fifth generation (GMTT1XX) produced from 2020 to 2023, represents GMC’s heavy-duty full-size pickup truck offering. This variant, featuring a Regular Cab and Long Bed configuration paired with the 6.6-liter Duramax Turbo-Diesel V8 engine producing 445 horsepower, occupied a significant position in the work-truck and heavy-towing segment of the American market. It catered to buyers needing substantial capability without the added expense or complexity of higher trim levels or crew cab configurations. This model year marked a substantial redesign for the Sierra HD line, focusing on increased capability, improved interior refinement, and advanced technology.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX) Regular Cab Long Bed |
| Type (Engine) | 6.6 Duramax TD V8 (445 Hp) SRW Automatic |
| Start of production | 2020 |
| End of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 2 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.4 kg/Hp, 135.4 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 375.4 Nm/tonne |
| Power | 445 Hp @ 2800 rpm |
| Power per litre | 67.4 Hp/l |
| Torque | 1234 Nm @ 1600 rpm (910.15 lb.-ft. @ 1600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax L5P |
| Engine displacement | 6604 cm3 (403 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 103 mm (4.06 in.) |
| Piston Stroke | 99 mm (3.9 in.) |
| Compression ratio | 16:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | OHV |
| Engine oil capacity | 9.5 l (10.04 US qt | 8.36 UK qt) |
| Coolant capacity | 29.1 l (30.75 US qt | 25.6 UK qt) |
| Kerb Weight | 3287 kg (7246.59 lbs.) |
| Max. weight | 4785 kg (10549.12 lbs.) |
| Max load | 1498 kg (3302.52 lbs.) |
| Fuel tank capacity | 106 l (28 US gal | 23.32 UK gal) |
| Permitted trailer load with brakes (12%) | 6577 kg (14499.8 lbs.) |
| Length | 5982 mm (235.51 in.) |
| Width including mirrors | 2076 mm (81.73 in.) |
| Height | 2056 mm (80.94 in.) |
| Wheelbase | 3595 mm (141.54 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 285 mm (11.22 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine. |
| Number of gears and type of gearbox | 10 gears, automatic transmission Allison |
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine, a staple of GMC and Chevrolet heavy-duty trucks, utilizes a cast iron block and aluminum cylinder heads. The L5P features a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The engine employs an overhead valve (OHV) valvetrain, a design choice prioritizing durability and low-end torque. A variable geometry turbocharger and intercooler work in tandem to maximize power and efficiency. Paired with the engine is the Allison 10-speed automatic transmission, a robust unit designed to handle the immense torque output of the Duramax. This transmission features electronically controlled shifts and multiple driving modes, including tow/haul, for optimized performance under load.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by this combination translate to impressive towing and hauling capabilities. While not as quick as gasoline-powered counterparts, the Duramax offers a broad, flat torque curve, making it exceptionally capable at low speeds and when carrying heavy loads. The 10-speed Allison transmission helps keep the engine in its optimal power band, providing smooth and confident acceleration. Compared to the 6.6L gasoline engine option, the Duramax provides significantly more torque, making it the preferred choice for demanding tasks. Compared to higher output Duramax variants, this 445hp version offers a balance between power and fuel economy, making it suitable for those who don’t consistently require maximum towing capacity.
Equipment & Trim Levels
The Regular Cab Long Bed 3500HD with the Duramax engine typically came in work truck (WT) or SLE trim levels. The WT trim focused on functionality, offering basic amenities like vinyl upholstery, manual windows and locks, and a basic audio system. The SLE trim added more comfort and convenience features, such as cloth upholstery, power windows and locks, keyless entry, and an upgraded infotainment system. Optional extras included a trailer brake controller, a fifth-wheel hitch preparation package, and various appearance packages. The interior, while functional, prioritized durability over luxury, reflecting the truck’s intended use.
Chassis & Braking
The Sierra 3500HD features a fully boxed frame designed for strength and rigidity. The front suspension utilizes coil springs and a double wishbone setup with a transverse stabilizer bar. The rear suspension employs a traditional leaf spring setup, optimized for load-carrying capacity. Braking duties are handled by ventilated discs at all four corners, providing ample stopping power even when heavily loaded. An Anti-lock Braking System (ABS) is standard. The rear axle is a solid axle, contributing to the truck’s robust towing capabilities.
Market Reception & Comparison
Critics generally praised the 2020-2023 Sierra 3500HD for its substantial towing capacity, comfortable ride (considering its heavy-duty nature), and refined interior compared to previous generations. The Duramax engine was consistently lauded for its power and efficiency. Compared to the gasoline engine option, the Duramax offered superior fuel economy when towing and a significantly higher resale value. Compared to competitors like the Ford Super Duty and Ram 3500, the Sierra 3500HD held its own in terms of capability and features, often being praised for its user-friendly infotainment system.
Legacy
The Duramax L5P engine has proven to be exceptionally reliable, with many examples exceeding 200,000 miles with proper maintenance. The Allison 10-speed transmission is also known for its durability. On the used market, these Sierra 3500HDs hold their value well, particularly those with the Duramax engine. They remain a popular choice for those seeking a capable and reliable heavy-duty truck for work or recreational purposes. The GMTT1XX generation represented a significant step forward for the Sierra HD line, solidifying its position as a leading contender in the heavy-duty truck segment.
