The GMC Sierra 3500HD, specifically the V (GMTT1XX) Crew Cab Long Bed configuration powered by the 6.6-liter Duramax TD V8 producing 445 horsepower, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2020 through 2023, this variant aimed to provide a balance of robust towing capability, comfortable interior space, and refined diesel performance. It occupied a premium position within the Sierra 3500HD lineup, catering to buyers needing substantial payload and towing capacity without sacrificing daily drivability. This model year marked a substantial refresh for the Sierra HD line, introducing updated styling, technology, and improved functionality.
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) SRW 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 kg/Hp, 125 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 346.6 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 | 3560 kg (7848.46 lbs.) |
| Max. weight | 5398 kg (11900.55 lbs.) |
| Max load | 1838 kg (4052.1 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 | 2079 mm (81.85 in.) |
| Height | 2049 mm (80.67 in.) |
| Wheelbase | 4369 mm (172.01 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 283 mm (11.14 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, 360×34 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 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 with the 6.6L Duramax diesel and 10-speed Allison automatic transmission represents GMC’s entry into the highest echelon of heavy-duty pickup trucks. Built on the GMTT1XX platform, this generation Sierra HD aimed to deliver increased capability, refinement, and technology compared to its predecessors. The Crew Cab configuration provides ample passenger space, while the Long Bed offers substantial cargo capacity. This particular variant, with its potent diesel engine and advanced transmission, was geared towards customers who frequently tow large trailers, haul heavy loads, or require a work truck capable of demanding tasks. It positioned itself above the gasoline-powered options and below the even more specialized trims focused on ultimate luxury.
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 cornerstone of GM’s heavy-duty truck strategy, known for its durability and impressive torque output. The L5P utilizes a cast iron block, aluminum cylinder heads, and a robust crankshaft designed to withstand the stresses of heavy-duty operation. The engine employs a high-pressure common rail direct fuel injection system, delivering fuel directly into the cylinders at extremely high pressures for optimized combustion. The turbocharger, coupled with an intercooler, forces more air into the engine, increasing power and efficiency. The overhead valve (OHV) valvetrain, while a traditional design, is known for its reliability and simplicity. Paired with the engine is the Allison 10-speed automatic transmission. This transmission is specifically designed to handle the high torque output of the Duramax engine and provides smooth, efficient shifting. The 10-speed configuration allows for closer gear ratios, keeping the engine in its optimal power band during acceleration and towing.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque produced by the Duramax engine and 10-speed Allison transmission translate into impressive real-world performance. While not designed for outright speed, this Sierra 3500HD excels at towing and hauling. The 10-speed transmission allows the engine to operate efficiently at highway speeds, contributing to relatively quiet and comfortable cruising. The close gear ratios provide ample power for accelerating with a load or climbing steep grades. Compared to the 6.6L gasoline engine option, the Duramax offers significantly more low-end torque, making it ideal for demanding tasks. Compared to older Duramax engines with fewer gears, the 10-speed Allison provides smoother shifts and improved fuel economy. The rear-wheel-drive configuration provides a traditional truck feel, while available four-wheel-drive enhances traction in challenging conditions.
Equipment & Trim Levels
The Sierra 3500HD Crew Cab Long Bed with the Duramax engine was typically offered in higher trim levels such as SLE, AT4, and Denali. Standard features generally included a user-friendly infotainment system with Apple CarPlay and Android Auto compatibility, a rearview camera, and a suite of safety features. Higher trims added features like leather upholstery, heated and ventilated front seats, a premium sound system, and advanced driver-assistance technologies such as adaptive cruise control and lane departure warning. Optional extras included a power sunroof, a rear-seat entertainment system, and various towing packages. The AT4 trim, in particular, focused on off-road capability with features like skid plates and off-road tuned suspension.
Chassis & Braking
The Sierra 3500HD features a robust chassis designed to handle heavy loads. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. This configuration provides a comfortable ride while maintaining excellent load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when towing. An Anti-lock Braking System (ABS) is standard, enhancing safety and control. The steering system utilizes a rack-and-pinion setup with electric power steering, providing precise and responsive handling. Tire sizes varied depending on the trim level and wheel size, ranging from 17-inch to 20-inch options.
Market Reception & Comparison
The GMC Sierra 3500HD with the Duramax diesel engine generally received positive reviews from critics. It was praised for its powerful engine, smooth transmission, comfortable ride, and spacious interior. 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 offered a compelling combination of capability, refinement, and technology. Some critics noted that the interior design, while improved, wasn’t as luxurious as some competitors. However, the Sierra’s overall value proposition and strong towing performance made it a popular choice among buyers.
Legacy
The Duramax L5P engine and Allison 10-speed transmission have proven to be a reliable and durable 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 specific maintenance procedures, the Duramax L5P has generally been considered a long-lasting engine when properly maintained. The 2020-2023 Sierra 3500HD represents a significant step forward in heavy-duty truck technology, offering a blend of power, refinement, and functionality that continues to appeal to buyers today.
