The GMC Sierra 3500HD, specifically the fifth generation (GMTT1XX) produced between 2020 and 2023, represents GMC’s heavy-duty full-size pickup truck offering. This variant, equipped with the 6.6-liter Duramax turbocharged diesel V8 engine producing 445 horsepower and paired with a 10-speed Allison automatic transmission, occupied a premium position within the Sierra 3500HD lineup, targeting buyers requiring substantial towing and hauling capabilities alongside a degree of refinement. The Crew Cab configuration with a standard bed further enhanced its practicality and appeal to both commercial and private users.
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) 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 | 7.7 kg/Hp, 129.5 Hp/tonne |
| Weight-to-torque ratio | 2.8 kg/Nm, 359 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 | 3437 kg (7577.29 lbs.) |
| Max. weight | 5330 kg (11750.64 lbs.) |
| Max load | 1893 kg (4173.35 lbs.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 9752 kg (21499.48 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 (Back) track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 284 mm (11.18 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine (ICE) drives the rear wheels. |
| 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 with the 6.6L Duramax diesel and 10-speed Allison automatic represents a significant evolution in GMC’s heavy-duty truck offerings. Built on the GMTT1XX platform, this generation aimed to balance robust capability with increased comfort and technology. Positioned as a premium work truck and capable daily driver, this configuration catered to owners needing substantial towing capacity, such as those hauling large trailers, fifth wheels, or heavy equipment. It sat above the gasoline-powered engine options and below the Denali trim, offering a compelling blend of power, features, and value.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine utilizes a cast iron block and aluminum cylinder heads, featuring direct injection and a variable geometry turbocharger. The common rail fuel injection system delivers fuel at extremely high pressures, optimizing combustion efficiency and power output. The overhead valve (OHV) valvetrain, while a traditional design, is known for its durability and reliability. The 10-speed Allison automatic transmission, a key upgrade from previous generations, provides a wider gear ratio spread, improving both acceleration and fuel economy. This transmission is electronically controlled and features a heavy-duty torque converter designed to handle the engine’s substantial output. The transmission’s programming is optimized for both towing and everyday driving, offering smooth shifts and responsive performance.
Driving Characteristics
The combination of the 445 horsepower and 910 lb-ft of torque delivered by the Duramax engine and the 10-speed Allison transmission results in a driving experience that is both powerful and refined. While not as quick off the line as some gasoline-powered trucks, the Sierra 3500HD excels in situations requiring substantial pulling power. The 10-speed transmission keeps the engine in its optimal power band, even when towing heavy loads. Compared to the 6.6L gasoline engine, the Duramax offers significantly more low-end torque, making it ideal for demanding tasks. Compared to older Duramax engines with 6-speed transmissions, the 10-speed provides smoother shifts and improved fuel efficiency. The ride quality, while still truck-like, is improved thanks to the refined suspension tuning and the transmission’s ability to select the appropriate gear for varying road conditions.
Equipment & Trim Levels
The Sierra 3500HD Crew Cab with the Duramax engine typically came standard with a robust set of features. These included air conditioning, power windows and locks, a touchscreen infotainment system with Apple CarPlay and Android Auto compatibility, and a rearview camera. Higher trim levels added features such as leather upholstery, heated and ventilated front seats, a premium sound system, and advanced safety technologies like blind-spot monitoring and rear cross-traffic alert. Optional extras included a power sunroof, a navigation system, and a bed liner. Interior upholstery generally consisted of cloth or vinyl in lower trims, with leather becoming standard on higher-spec models. The dashboard layout was functional and driver-focused, with clearly labeled controls and a user-friendly interface.
Chassis & Braking
The Sierra 3500HD’s chassis is built for heavy-duty use, featuring a fully boxed frame and robust suspension components. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs leaf springs. The rear axle is a heavy-duty unit designed to handle significant loads. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when towing. The front brakes measure 350x40mm, while the rear brakes are 360x34mm. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. Stabilizer bars are included to reduce body roll during cornering.
Market Reception & Comparison
The 2020-2023 GMC Sierra 3500HD with the Duramax diesel engine received generally positive reviews from automotive critics. The engine was praised for its power and efficiency, while the 10-speed Allison transmission was lauded for its smooth operation and improved fuel economy. Critics noted that the Sierra 3500HD offered a comfortable ride and a well-appointed interior, making it a viable option for both work and personal use. Compared to the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as offering a more refined driving experience, although some critics found the interior design less bold than its competitors. Fuel economy, while improved with the 10-speed transmission, remained relatively low compared to lighter-duty trucks.
Legacy
The Duramax L5P engine and 10-speed Allison transmission pairing has proven to be a reliable and durable powertrain. While long-term reliability data is still emerging, early indications suggest that this combination is well-engineered and capable of withstanding years of heavy use. On the used car market, these Sierra 3500HD models hold their value well, particularly those with lower mileage and well-maintained service records. The demand for diesel-powered heavy-duty trucks remains strong, ensuring that this variant will continue to be a popular choice for buyers seeking a capable and reliable workhorse for years to come. The GMTT1XX platform represents a significant step forward in heavy-duty truck design, offering a blend of capability, comfort, and technology that sets it apart from previous generations.
