The GMC Sierra 2500HD V (GMTT1XX) Crew Cab Standard Bed, equipped with the 6.6-liter Duramax TD V8 engine producing 445 horsepower, represents a significant iteration in GMC’s heavy-duty truck lineup. Produced from 2020 to 2023, this variant occupied a premium position within the Sierra 2500HD range, targeting buyers requiring substantial towing capacity and robust performance. It builds upon the foundation of the GMTT1XX platform, a chassis designed for enhanced strength and capability compared to its predecessors. This particular configuration, combining the powerful Duramax diesel with a ten-speed automatic transmission, became a popular choice for both commercial and private users needing a capable work truck or a powerful personal vehicle.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD 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 | 7.6 kg/Hp, 132 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 366.2 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 | 3370 kg (7429.58 lbs.) |
| Max. weight | 4899 kg (10800.45 lbs.) |
| Max load | 1529 kg (3370.87 lbs.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 8392 kg (18501.19 lbs.) |
| Length | 6352 mm (250.08 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2027 mm (79.8 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) | 257 mm (10.12 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 | Cone worm with recirculation balls |
| Power steering | Hydraulic 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 |
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD variant lies the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a cornerstone of GMC’s heavy-duty offerings, renowned for its durability and substantial torque output. The L5P utilizes a cast iron block and aluminum cylinder heads, contributing to its robust construction. The engine employs a diesel common rail fuel injection system, delivering highly pressurized fuel directly into the cylinders for efficient combustion. The overhead valve (OHV) valvetrain, while a more traditional design, is known for its reliability and simplicity. A single variable geometry turbocharger, coupled with an intercooler, maximizes power and efficiency. The ten-speed Allison automatic transmission, a key component of this configuration, is specifically tuned to handle the engine’s immense torque. This transmission features electronically controlled shifts and a wide gear ratio spread, optimizing both towing performance and fuel economy.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by the Duramax engine and Allison transmission combination translate into impressive real-world performance. While not designed for outright speed, this Sierra 2500HD excels at hauling heavy loads and navigating challenging terrain. The ten-speed transmission allows the engine to operate within its optimal power band more frequently, providing strong acceleration even when towing. Compared to the 6.6L gasoline engine option, the Duramax offers significantly more low-end torque, making it ideal for demanding tasks. Compared to lower-output diesel variants, the 445 hp version provides a noticeable increase in power for highway passing and merging. The gear ratios are optimized for towing, with lower gears providing ample pulling power and higher gears maintaining comfortable cruising speeds.
Equipment & Trim Levels
The Crew Cab Standard Bed configuration typically came well-equipped, positioning it as a mid-to-upper trim level within the Sierra 2500HD lineup. Standard features generally included a user-friendly infotainment system with a touchscreen display, Apple CarPlay and Android Auto compatibility, and a premium audio system. Interior upholstery typically consisted of cloth or leather, depending on optional packages. Available options included a power-adjustable driver’s seat, heated and ventilated front seats, a sunroof, and advanced safety features such as lane departure warning and automatic emergency braking. The standard bed length provided a practical cargo area for various hauling needs.
Chassis & Braking
The GMTT1XX platform features a fully boxed frame constructed from high-strength steel, providing a solid foundation for heavy-duty applications. The front suspension utilizes a coil spring, double wishbone design with a transverse stabilizer bar, offering a comfortable ride and predictable handling. The rear suspension employs a traditional leaf spring setup, optimized for load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, with larger rotors providing ample stopping power. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. The hydraulic power steering system provides responsive and precise steering feel.
Market Reception & Comparison
The 6.6-liter Duramax diesel engine consistently received positive reviews for its power, reliability, and fuel efficiency. Critics praised the Allison ten-speed automatic transmission for its smooth shifting and ability to maximize the engine’s potential. Compared to gasoline-powered Sierra 2500HD models, the diesel variant offered superior fuel economy, particularly when towing. While the initial cost was higher, the long-term benefits of reduced fuel consumption and increased resale value often outweighed the price difference. Compared to other heavy-duty trucks in its class, the GMC Sierra 2500HD with the Duramax engine was often considered a top contender, offering a compelling combination of performance, capability, and refinement.
Legacy
The Duramax L5P engine, paired with the Allison transmission, has proven to be a remarkably durable and reliable powertrain. These trucks have maintained strong resale values in the used car market, reflecting their reputation for longevity and capability. Properly maintained examples continue to provide years of dependable service, making them a popular choice for buyers seeking a robust and capable heavy-duty truck. While newer generations of the Sierra 2500HD have introduced further advancements in technology and efficiency, the 2020-2023 models with the 6.6-liter Duramax remain a highly regarded and sought-after configuration.
