The GMC Sierra 2500HD, specifically the V (GMTT1XX) Crew Cab Long Bed configuration powered by the 6.6-liter Duramax Turbo Diesel 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 for the American truck buyer. It slots into the Sierra 2500HD lineup as a premium offering, positioned above the gasoline-powered engines and often featuring more standard equipment than base trims.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Crew Cab Long 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, 124.4 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 345 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 | 3577 kg (7885.94 lbs.) |
| Max. weight | 5158 kg (11371.44 lbs.) |
| Max load | 1581 kg (3485.51 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 | 6759 mm (266.1 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2023 mm (79.65 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) | 256 mm (10.08 in.) |
| Drivetrain Architecture | All wheel drive (4×4). Internal Combustion engine. The ICE drives the rear wheels permanently, and the front wheels are driven through an electrically or mechanically operated clutch if necessary. |
| 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 truck offerings, known 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 common-rail direct 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 and efficiency. The overhead valve (OHV) valvetrain, while a more traditional design, is favored for its simplicity and reliability in heavy-duty applications. Paired with the engine is the Allison 10-speed automatic transmission, a heavy-duty unit specifically designed to handle the immense torque produced by the Duramax engine. This transmission features electronically controlled shifts and a lock-up torque converter for improved fuel economy and responsiveness.
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 focused on effortless towing and hauling. The 10-speed transmission allows for tightly spaced gear ratios, keeping the engine within its optimal power band during acceleration and maintaining comfortable cruising speeds. While not a sports truck, the Sierra 2500HD offers surprisingly responsive acceleration for its size and weight. Compared to the gasoline-powered 6.6L V8 option, the Duramax provides significantly more low-end torque, making it ideal for demanding tasks. Compared to the 6.6L Duramax in earlier generations, the L5P offers improved refinement and reduced noise, vibration, and harshness (NVH). The automatic transmission, while efficient, doesn’t offer the direct control of a manual transmission, but it simplifies operation for drivers primarily focused on work or long-distance towing.
Equipment & Trim Levels
The Crew Cab Long Bed configuration provides ample interior space for passengers and cargo. Standard features typically 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, such as Denali, added premium features like leather upholstery, heated and ventilated seats, a premium sound system, and advanced safety technologies like adaptive cruise control and lane departure warning. Optional extras included a power sunroof, a navigation system, and various towing packages designed to enhance the truck’s capabilities.
Chassis & Braking
The Sierra 2500HD features a fully boxed frame designed for strength and rigidity. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. This configuration is optimized for carrying heavy loads and maintaining stability. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) is standard. The rear axle ratios varied depending on the specific configuration, influencing both towing capacity and fuel economy.
Market Reception & Comparison
The 2020-2023 GMC Sierra 2500HD with the Duramax diesel and 10-speed automatic received generally positive reviews. Critics praised its powerful engine, smooth transmission, and comfortable ride. Fuel economy, while improved over previous generations, remained a consideration for some buyers. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD was often seen as offering a more refined interior and a more sophisticated driving experience. The Duramax engine’s reputation for reliability was a significant selling point, although diesel engines generally require more expensive maintenance than their gasoline counterparts.
Legacy
The Duramax L5P engine has proven to be a durable and reliable powerplant, and the 10-speed Allison transmission has also demonstrated strong performance. In the used car market, these Sierra 2500HD models hold their value well, particularly those that have been well-maintained and have a documented service history. The combination of power, capability, and relative refinement makes this variant a desirable choice for buyers seeking a heavy-duty truck for work or recreational purposes. Regular maintenance, including oil changes and fuel filter replacements, is crucial for ensuring the long-term reliability of the Duramax engine and Allison transmission.
