Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX) Crew Cab Standard Bed |
| Type (Engine) | 6.6 Duramax TD V8 (445 Hp) 4WD 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, 124.5 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 345.4 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 | 3573 kg (7877.12 lbs.) |
| Max. weight | 5489 kg (12101.17 lbs.) |
| Max load | 1916 kg (4224.06 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 | 6352 mm (250.08 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2054 mm (80.87 in.) |
| Wheelbase | 4037 mm (158.94 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 284 mm (11.18 in.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front wheels engaged via clutch. |
| 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 |
The 2020-2023 GMC Sierra 3500HD Crew Cab equipped with the 6.6L Duramax diesel and 10-speed Allison automatic transmission represents a significant advancement in GMC’s heavy-duty truck lineup. Built on the GMTT1XX platform, this generation prioritized capability, technology, and interior refinement. The combination of the powerful Duramax engine, the advanced Allison transmission, and the four-wheel-drive system made this variant a top choice for buyers needing substantial towing and hauling capacity. The Crew Cab configuration offered ample space for passengers, while the standard bed provided a practical cargo area. This truck aimed to bridge the gap between a purely work-focused vehicle and a more comfortable, daily-driver capable pickup.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. 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 Bosch common rail fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The turbocharger, coupled with an intercooler, provides increased air density for enhanced power output. The engine employs an overhead valve (OHV) valvetrain, a design choice favored for its durability and low-end torque characteristics. The 10-speed Allison automatic transmission is a key component, offering a wide gear ratio spread for optimal performance and efficiency. This transmission is known for its durability and smooth shifting, and it’s specifically tuned to handle the high torque output of the Duramax engine. The transmission features electronically controlled shifts and multiple driving modes.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by this powertrain combination translate into impressive real-world performance. While not designed for outright speed, the Sierra 3500HD excels at accelerating with heavy loads. The 10-speed Allison transmission keeps the engine in its optimal power band, providing strong acceleration even when towing. Compared to the gasoline-powered variants, the Duramax diesel offers significantly more low-end torque, making it ideal for hauling and towing. Compared to earlier Duramax engines, the L5P benefits from the wider gear ratios of the 10-speed Allison, resulting in improved fuel economy and reduced engine noise at highway speeds. The four-wheel-drive system provides enhanced traction in various conditions, making it suitable for both on-road and off-road use.
Equipment & Trim Levels
The Sierra 3500HD offered a range of trim levels, with this Duramax/Allison combination typically found on the SLT, AT4, and Denali trims. Standard features 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 such as leather upholstery, heated and ventilated seats, a premium sound system, and advanced driver-assistance technologies like 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. Heavy-duty shock absorbers and a transverse stabilizer bar help to control body roll and provide a comfortable ride. The braking system consists of ventilated discs at all four wheels, with larger rotors and calipers on the rear axle to accommodate the increased weight. An Anti-lock Braking System (ABS) is standard, providing enhanced stopping power and control. The steering system utilizes a rack-and-pinion design with electric power steering, offering precise and responsive handling.
Market Reception & Comparison
The GMC Sierra 3500HD with the Duramax diesel and Allison transmission received generally positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, and comfortable ride. Compared to the Ford Super Duty and Ram 3500, the Sierra 3500HD was often noted for its refined interior and advanced technology. Fuel economy, while respectable for a heavy-duty truck, was comparable to its competitors. Reliability has been generally good, although some owners have reported issues with the diesel particulate filter. The Duramax/Allison combination typically commanded a higher price than the gasoline-powered variants, reflecting its increased capability and premium features.
Legacy
The 2020-2023 GMC Sierra 3500HD with the 6.6L Duramax diesel and 10-speed Allison automatic has established itself as a reliable and capable heavy-duty truck. The L5P Duramax engine is known for its longevity and relatively low maintenance costs, making it a desirable powertrain in the used car market. These trucks continue to hold their value well, particularly those in good condition with low mileage. The combination of power, technology, and comfort has made this variant a popular choice among truck enthusiasts and commercial users alike, solidifying its place as a significant offering in the heavy-duty pickup truck segment.
