The GMC Sierra 2500HD V (GMTT1XX) Regular Cab Long Bed, equipped with 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 configuration catered to buyers needing substantial towing and hauling capacity, while prioritizing diesel efficiency and durability. This particular variant occupied a strong position within the Sierra 2500HD lineup, serving as a workhorse option for those prioritizing capability over luxury, though still offering a comfortable and well-equipped cabin. It was positioned above the gasoline-powered engine options and below the more premium trim levels offering additional features.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Regular Cab Long 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 | 2 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.1 kg/Hp, 140.8 Hp/tonne |
| Weight-to-torque ratio | 2.6 kg/Nm, 390.4 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 | 3161 kg (6968.81 lbs.) |
| Max. weight | 4785 kg (10549.12 lbs.) |
| Max load | 1624 kg (3580.31 lbs.) |
| Fuel tank capacity | 106 l (28 US gal | 23.32 UK gal) |
| Permitted trailer load with brakes (12%) | 6577 kg (14499.8 lbs.) |
| Length | 5982 mm (235.51 in.) |
| Width including mirrors | 2076 mm (81.73 in.) |
| Height | 2030 mm (79.92 in.) |
| Wheelbase | 3595 mm (141.54 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 | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 10 gears, automatic transmission Allison |
Powertrain & Engine Architecture
The heart of this Sierra 2500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a cornerstone of GMC’s heavy-duty lineup, known for its robust construction and impressive torque output. The L5P utilizes a cast iron block and aluminum cylinder heads, contributing to its longevity. The engine employs a diesel commonrail fuel injection system, delivering highly pressurized fuel directly into the cylinders for efficient combustion. The turbocharger, coupled with an intercooler, forces more air into the engine, boosting power and torque. The overhead valve (OHV) valvetrain, while a more traditional design, is known for its reliability and simplicity. 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 efficiency.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by this combination translate into exceptional towing and hauling capabilities. While not designed for outright speed, the Sierra 2500HD with this powertrain offers ample power for merging onto highways and maintaining speed even when heavily loaded. The 10-speed Allison transmission is well-tuned, providing smooth and relatively quick shifts. Compared to the gasoline-powered 6.6L V8, the Duramax offers significantly more low-end torque, making it ideal for towing. Compared to the 6.6L Duramax in earlier generations, the L5P provides a noticeable increase in horsepower and torque. The automatic transmission, while convenient, doesn’t offer the same level of control as a manual transmission, but it excels in providing a comfortable and effortless driving experience, especially in stop-and-go traffic.
Equipment & Trim Levels
The Regular Cab Long Bed configuration typically came standard with features geared towards work-truck functionality. This included vinyl upholstery, a basic infotainment system with a touchscreen display, and air conditioning. However, options were available to upgrade the interior with features like leather upholstery, heated seats, a premium audio system, and advanced safety technologies such as lane departure warning and automatic emergency braking. The exterior typically featured black bumpers and grille accents, though chrome options were available. The long bed provided ample cargo space, making it suitable for a variety of hauling needs.
Chassis & Braking
The Sierra 2500HD utilizes a body-on-frame construction, providing a robust and durable platform. The front suspension consists of coil springs and a double wishbone setup, while the rear suspension employs leaf springs. This configuration is designed to handle heavy loads and provide a comfortable ride. Braking duties are handled by ventilated discs at all four corners, providing ample stopping power. The truck is equipped with an anti-lock braking system (ABS) for enhanced safety. Hydraulic power steering provides responsive and precise steering control.
Market Reception & Comparison
The GMC Sierra 2500HD with the 6.6-liter Duramax and Allison transmission was generally well-received by critics and consumers alike. It was praised for its exceptional towing capacity, strong fuel economy for a heavy-duty truck, and overall reliability. Compared to the gasoline-powered Sierra 2500HD, the Duramax offered superior torque and fuel efficiency, making it a popular choice for those who frequently tow or haul heavy loads. 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 value.
Legacy
The Duramax L5P engine has proven to be a remarkably reliable powertrain. With proper maintenance, these engines are known to exceed 200,000 miles without major issues. On the used car market, the 2020-2023 Sierra 2500HD with the Duramax engine holds its value well, due to its reputation for durability and capability. The Allison transmission is also highly regarded for its reliability and longevity. This combination remains a popular choice for buyers seeking a capable and dependable heavy-duty pickup truck.
