The GMC Sierra 3500HD, specifically the V (GMTT1XX) Crew Cab Long Bed configuration with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2020 through 2023, this variant catered to buyers needing substantial towing and hauling capabilities, positioning itself as a premium workhorse within the Sierra 3500HD lineup. It was part of the fourth generation of the Sierra HD series, known for its increased strength, refined interior, and advanced technology compared to its predecessors.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX) Crew Cab Long Bed |
| Type (Engine) | 6.6 Duramax TD V8 (445 Hp) DRW Automatic |
| Start of production | 2020 |
| End of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.2 kg/Hp, 121.6 Hp/tonne |
| Weight-to-torque ratio | 3 kg/Nm, 337.1 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 | 29.1 l (30.75 US qt | 25.6 UK qt) |
| Kerb Weight | 3661 kg (8071.12 lbs.) |
| Max. weight | 6350 kg (13999.35 lbs.) |
| Max load | 2689 kg (5928.23 lbs.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 9072 kg (20000.34 lbs.) |
| Length | 6759 mm (266.1 in.) |
| Width including mirrors | 2457 mm (96.73 in.) |
| Height | 2033 mm (80.04 in.) |
| Wheelbase | 4369 mm (172.01 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1905 mm (75 in.) |
| Ride height (ground clearance) | 264 mm (10.39 in.) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 10 gears, automatic transmission Allison |
| Front suspension | Coil spring, Double wishbone, Transverse stabilizer |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 350×40 mm |
| Rear brakes | Ventilated discs, 355×40 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 235/80 R17; 265/70 R17; 245/75 R17; 265/70 R18; 265/60 R20 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 20 |
INTRODUCTION
The 2020-2023 GMC Sierra 3500HD Crew Cab Long Bed equipped with the 6.6L Duramax diesel and 10-speed Allison automatic transmission was designed for customers who demanded maximum capability. This truck was built on the GMTT1XX platform, a fully-boxed frame designed for increased rigidity and reduced weight. The Crew Cab configuration offered spacious seating for five passengers, while the Long Bed provided ample cargo space. This particular variant occupied the upper echelon of the Sierra 3500HD range, appealing to those who frequently tow large trailers, haul heavy loads, or require a robust and reliable work truck.
Powertrain & Engine Architecture
At the heart of this Sierra 3500HD lies the Duramax L5P 6.6-liter turbocharged diesel V8 engine. This engine is a testament to modern diesel technology, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly. The L5P utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The turbocharger, coupled with an intercooler, provides increased air intake, boosting power and efficiency. The engine produces 445 horsepower at 2800 rpm and a massive 910 lb-ft of torque at 1600 rpm. The Allison 10-speed automatic transmission is specifically tuned to handle the engine’s substantial torque output. This transmission features electronically controlled shifts and a wide gear ratio spread, optimizing both towing performance and fuel economy. The transmission’s robust construction ensures durability under heavy loads.
Driving Characteristics
The combination of the high-output Duramax diesel and the 10-speed Allison transmission delivers a commanding driving experience. Acceleration, while not sporty, is surprisingly brisk for a heavy-duty truck. The 10-speed transmission allows the engine to remain in its optimal power band, providing strong pulling power from a standstill and during highway passing maneuvers. The gear ratios are well-spaced, minimizing gear hunting and providing smooth, confident shifts. Compared to the 6.6L gasoline engine option, the Duramax offers significantly more torque, making it ideal for towing. Compared to lower-output diesel variants, this 445hp version provides a noticeable increase in horsepower, improving overall responsiveness. The dual rear wheels (DRW) configuration enhances stability when towing heavy loads.
Equipment & Trim Levels
The Sierra 3500HD Crew Cab Long Bed with the Duramax engine typically came standard with a comprehensive list of features. These included a large infotainment touchscreen with Apple CarPlay and Android Auto compatibility, a rearview camera, and a suite of driver-assistance technologies such as automatic emergency braking and lane departure warning. Interior appointments typically featured comfortable cloth or leather upholstery, depending on the trim level. Optional extras included a premium Bose audio system, heated and ventilated front seats, a power-adjustable steering column, and a variety of trailering packages with features like integrated trailer brake controllers and trailer sway control. Higher trim levels, such as Denali, added even more luxurious features, including unique exterior styling, upgraded interior materials, and advanced technology features.
Chassis & Braking
The Sierra 3500HD’s chassis is engineered for heavy-duty use. The fully-boxed frame provides a solid foundation, while the coil-spring front suspension and leaf-spring rear suspension are designed to handle substantial payloads. The rear axle is heavy-duty, capable of supporting significant weight. Braking duties are handled by ventilated disc brakes at all four corners, providing ample stopping power even when towing. The anti-lock braking system (ABS) helps maintain control during emergency braking situations. The DRW configuration provides increased stability and braking performance when hauling heavy loads. Steering is rack-and-pinion with electric power assist, offering precise control and a comfortable driving experience.
Market Reception & Comparison
The GMC Sierra 3500HD with the Duramax diesel engine consistently received positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, comfortable ride, and impressive towing capabilities. Fuel economy, while not exceptional, was considered competitive for a heavy-duty truck. Compared to the Ford Super Duty and Ram 3500, the Sierra 3500HD was often lauded for its refined interior and advanced technology. The Duramax engine was generally regarded as being as reliable, if not more so, than its competitors’ diesel offerings. However, the initial cost of the Duramax-equipped Sierra 3500HD was higher than gasoline-powered models and some lower-output diesel variants.
Legacy
The Duramax L5P engine paired with the Allison 10-speed transmission has proven to be a durable and reliable powertrain combination. These trucks have maintained strong resale values in the used car market, reflecting their reputation for dependability and capability. While diesel engines require more diligent maintenance than gasoline engines, the Duramax L5P has generally been considered a long-lasting and trouble-free engine when properly maintained. The 2020-2023 Sierra 3500HD with this powertrain continues to be a popular choice for those seeking a heavy-duty truck capable of handling demanding tasks.
