The GMC Sierra 2500HD, specifically the V (GMTT1XX) Double Cab Standard Bed configuration powered by the 6.6-liter Duramax TD V8 engine producing 445 horsepower, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2020 to 2023, this variant occupied a premium position within the Sierra 2500HD lineup, targeting buyers requiring substantial towing and hauling capabilities combined with a degree of refinement. It was part of the fourth generation of the Sierra HD series, known for its robust construction and advanced technology.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Double 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 | 7.4 kg/Hp, 134.9 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 374.1 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 capacity | 29.1 l (30.75 US qt | 25.6 UK qt) |
| Kerb Weight | 3299 kg (7273.05 lbs.) |
| Max. weight | 4854 kg (10701.24 lbs.) |
| Max load | 1555 kg (3428.19 lbs.) |
| Fuel tank capacity | 111 l (29.32 US gal | 24.42 UK gal) |
| Permitted trailer load with brakes (12%) | 6577 kg (14499.8 lbs.) |
| Length | 6107 mm (240.43 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2031 mm (79.96 in.) |
| Wheelbase | 3795 mm (149.41 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 259 mm (10.2 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine (ICE) drives the rear wheels. |
| 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 | 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
The heart of this Sierra 2500HD variant is the 6.6-liter Duramax L5P turbodiesel V8 engine. This engine is a significant departure from earlier Duramax designs, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly designed for high torque output. The L5P utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The engine employs an overhead valve (OHV) valvetrain, a design choice prioritizing low-end torque and durability over high-revving performance. A single variable geometry turbocharger (VGT) with an intercooler provides forced induction, boosting power and efficiency. The engine is paired with a heavy-duty 10-speed Allison automatic transmission, specifically tuned for the demands of towing and hauling. This transmission offers smooth shifting and precise control, maximizing the engine’s torque output.
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 accelerating with heavy loads. The 10-speed Allison transmission’s gear ratios are optimized for both towing and highway cruising. Lower gears provide ample torque for starting and climbing hills with trailers, while higher gears allow for relaxed and fuel-efficient operation at highway speeds. Compared to gasoline-powered Sierra 2500HD models, the diesel offers significantly more low-end torque, making it far more capable when towing. Compared to the 6.6L gasoline engine, the diesel provides a more relaxed driving experience under load, requiring less frequent downshifting. The ride quality, even unladen, is relatively comfortable for a heavy-duty truck, though it’s still noticeably firmer than lighter-duty pickups.
Equipment & Trim Levels
The Double Cab Standard Bed configuration typically came well-equipped, positioning it as a mid-to-upper trim level. Standard features generally 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 like leather upholstery, heated and ventilated front seats, a premium sound system, and advanced safety technologies such as lane departure warning and automatic emergency braking. Optional extras included a sunroof, a navigation system, and various towing packages. Interior materials were generally durable and functional, reflecting the truck’s work-oriented nature, but with a degree of comfort and refinement.
Chassis & Braking
The Sierra 2500HD features a fully boxed frame constructed from high-strength steel, providing a solid foundation for heavy-duty use. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs leaf springs. This configuration prioritizes load-carrying capacity and stability. Braking duties are handled by ventilated disc brakes at all four corners, 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. Steering is accomplished via a hydraulic power steering system, offering a responsive and predictable feel.
Market Reception & Comparison
The 6.6-liter Duramax diesel engine consistently received positive reviews for its power, torque, and reliability. Critics praised the Sierra 2500HD’s towing and hauling capabilities, as well as its comfortable ride quality. Fuel economy, while not exceptional, was considered competitive for a heavy-duty truck. Compared to the gasoline-powered Sierra 2500HD, the diesel variant commanded a higher price but offered significantly lower operating costs when used for demanding tasks. The Duramax/Allison combination was often favored by professionals and enthusiasts who required a truck capable of handling heavy loads on a regular basis.
Legacy
The Duramax L5P engine has proven to be a durable and reliable powerplant, with many examples exceeding 200,000 miles with proper maintenance. On the used car market, Sierra 2500HD models equipped with this engine and transmission combination hold their value well, reflecting their reputation for dependability and capability. Regular maintenance, including oil changes and fuel filter replacements, is crucial for ensuring the longevity of this powertrain. The GMTT1XX generation Sierra 2500HD, particularly the Duramax-equipped models, remains a popular choice for those seeking a capable and reliable heavy-duty pickup truck.
