The GMC Sierra 2500HD, in its fifth generation (GMTT1XX), represents GMC’s heavy-duty full-size pickup truck offering. Produced from 2020 to 2023, the Double Cab Standard Bed configuration with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower and paired with a 10-speed automatic transmission was a popular choice for buyers needing substantial towing and hauling capability. This variant occupied a premium position within the 2500HD lineup, offering a balance of power, refinement, and functionality aimed at both commercial users and private owners requiring serious truck performance.
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) 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 | 7.7 kg/Hp, 129.3 Hp/tonne |
| Weight-to-torque ratio | 2.8 kg/Nm, 358.6 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 | 3441 kg (7586.11 lbs.) |
| Max. weight | 4990 kg (11001.07 lbs.) |
| Max load | 1549 kg (3414.96 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 | 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 |
Powertrain & Engine Architecture
The heart of this Sierra 2500HD variant is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a significant evolution of the Duramax design, 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 turbocharger, coupled with an intercooler, provides increased air density for enhanced power and efficiency. The engine employs an overhead valve (OHV) valvetrain, a design choice prioritizing durability and low-end torque. The 10-speed Allison automatic transmission is a key component, providing a wide gear ratio spread for optimal towing performance and fuel economy. This transmission features electronically controlled shifts and a lock-up torque converter for improved efficiency.
Driving Characteristics
The combination of the 445 horsepower and 910 lb-ft of torque delivered by the Duramax engine and managed by the 10-speed Allison transmission results in impressive driving characteristics. Acceleration, while not sporty, is strong and confident, even when heavily loaded. The transmission’s numerous gears keep the engine within its optimal power band, providing responsive performance in a variety of driving situations. Compared to the gasoline-powered 6.6L V8 option, the Duramax offers significantly more low-end torque, making it ideal for towing and hauling heavy loads. While the gasoline engine might feel more responsive at higher RPMs, the diesel’s abundant torque provides a more effortless experience when working. Compared to the 2500HD models equipped with the 6.6L Duramax and a 6-speed automatic, the 10-speed offers smoother shifts and improved fuel economy.
Equipment & Trim Levels
The Double Cab Standard Bed 2500HD with the Duramax engine typically came well-equipped, often falling into the mid-to-upper trim levels like the SLE or AT4. 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 trims added features such as leather upholstery, heated and ventilated front seats, a premium audio system, and advanced safety technologies like blind-spot monitoring and rear cross-traffic alert. 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 with a transverse stabilizer bar, while the rear suspension employs a traditional leaf spring setup. This configuration provides a comfortable ride while maintaining excellent load-carrying capacity. Braking duties are handled by ventilated discs at all four corners, providing ample stopping power even when towing heavy loads. An Anti-lock Braking System (ABS) is standard. The robust chassis and braking system are designed to handle the substantial weight and torque output of the Duramax engine.
Market Reception & Comparison
The Duramax-equipped Sierra 2500HD received generally positive reviews from automotive critics. The engine was praised for its power, torque, and refinement, while the 10-speed Allison transmission was lauded for its smooth shifting and improved fuel economy compared to older transmissions. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD was often seen as offering a good balance of capability, comfort, and technology. Fuel economy, while still relatively low compared to lighter vehicles, was competitive within the heavy-duty truck segment. Reliability was generally good, although diesel engines can be more complex and potentially more expensive to maintain than gasoline engines.
Legacy
The GMTT1XX generation Sierra 2500HD, particularly the 6.6L Duramax/10-speed automatic combination, has proven to be a durable and capable truck. On the used car market, these models hold their value relatively well, reflecting their reputation for reliability and towing prowess. The L5P Duramax engine is known for its longevity, and with proper maintenance, can provide many years of dependable service. The 10-speed Allison transmission has also proven to be a robust and reliable unit. This variant remains a popular choice for buyers seeking a heavy-duty truck capable of handling demanding tasks.
