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 combined with the refinement of a modern diesel powertrain. This variant occupied a premium position within the Sierra 2500HD lineup, offering a balance between capability and features, appealing to both commercial users and individual truck enthusiasts.
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) 4WD 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 | 7.4 kg/Hp, 134.7 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 373.6 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 | 3303 kg (7281.87 lbs.) |
| Max. weight | 4944 kg (10899.65 lbs.) |
| Max load | 1641 kg (3617.79 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 | All wheel drive (4×4). Internal Combustion engine. The ICE drives the rear wheels permanently, with the front wheels engaged via an electrically or mechanically operated clutch. |
| 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 | 235/80 R17; 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 |
INTRODUCTION
The 2020-2023 GMC Sierra 2500HD Regular Cab Long Bed with the 6.6L Duramax diesel and 10-speed Allison automatic transmission represents a significant evolution in GMC’s heavy-duty truck offerings. Built on the GMTT1XX platform, this generation aimed to provide increased capability, refinement, and technology compared to its predecessors. The Regular Cab configuration, paired with the long bed, specifically targeted customers prioritizing maximum cargo space and work-truck functionality. This variant stood out due to its potent diesel engine, offering substantial torque for demanding tasks, and the advanced Allison transmission, known for its durability and smooth shifting.
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD lies the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a testament to modern diesel technology, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly. The L5P utilizes a Bosch common-rail fuel injection system, delivering highly precise fuel metering for optimal combustion and efficiency. The turbocharger, coupled with an intercooler, provides increased air intake, boosting power and torque output. The engine’s OHV valvetrain contributes to its durability and low-end torque characteristics. The 10-speed Allison automatic transmission is a key component, designed to handle the engine’s substantial torque and provide smooth, efficient power delivery. This transmission features electronically controlled shifts and multiple driving modes, optimizing performance for various conditions.
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 capability and control. While not designed for outright speed, this Sierra 2500HD excels in towing and hauling. The 10-speed transmission keeps the engine within its optimal power band, providing strong acceleration even when heavily loaded. Compared to gasoline-powered versions of the Sierra 2500HD, the diesel offers significantly more low-end torque, making it easier to start heavy loads and maintain speed on inclines. The automatic transmission provides convenient operation, especially in stop-and-go traffic or when navigating challenging terrain. The gear ratios are optimized for both towing and fuel efficiency, allowing for comfortable highway cruising.
Equipment & Trim Levels
The Sierra 2500HD Regular Cab Long Bed with the Duramax diesel typically came standard with a functional, work-oriented interior. Standard features included a basic infotainment system with a touchscreen display, Bluetooth connectivity, and a rearview camera. The interior upholstery was typically vinyl or cloth, designed for durability and ease of cleaning. Higher trim levels offered upgrades such as leather upholstery, heated and ventilated front seats, and a premium audio system. Optional extras included a navigation system, a power sunroof, and various driver-assistance features like lane departure warning and automatic emergency braking. The Regular Cab configuration prioritized functionality over luxury, offering a spacious work environment for the driver and passenger.
Chassis & Braking
The Sierra 2500HD’s chassis is built for heavy-duty use, featuring a robust frame and heavy-duty suspension components. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. This configuration provides a comfortable ride while maintaining excellent load-carrying capacity. The braking system consists of ventilated disc brakes on all four wheels, providing ample stopping power even when towing heavy loads. An Anti-lock Braking System (ABS) is standard, enhancing safety and control. The steering system utilizes a hydraulic power steering system, offering precise and responsive handling.
Market Reception & Comparison
The GMC Sierra 2500HD with the Duramax diesel and Allison transmission generally received positive reviews from critics and consumers alike. The engine was praised for its power, torque, and refinement, while the transmission was lauded for its smooth shifting and durability. Compared to other heavy-duty trucks in its class, such as the Ford Super Duty and Ram 2500, the Sierra 2500HD offered a competitive combination of capability, technology, and comfort. Fuel economy was generally considered to be good for a heavy-duty diesel truck, although it varied depending on driving conditions and load. Reliability was also a strong point, with the Duramax engine and Allison transmission proving to be exceptionally durable over the long term.
Legacy
The 2020-2023 GMC Sierra 2500HD with the 6.6L Duramax diesel and Allison transmission has established a strong reputation for reliability and capability. These trucks continue to hold their value well in the used car market, reflecting their durability and desirability. The Duramax L5P engine is known for its longevity, and with proper maintenance, can easily exceed 200,000 miles. The Allison transmission is equally robust, capable of handling years of heavy use. This combination makes this Sierra 2500HD a popular choice for buyers seeking a dependable and capable heavy-duty truck for work or recreational purposes.
