The GMC Sierra 2500HD V (GMTT1XX) Double Cab Long Bed, equipped with the 6.6-liter V8 engine producing 401 horsepower, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2020 to 2023, this variant occupied a strong position within the Sierra 2500HD lineup, catering to buyers needing substantial towing and hauling capabilities without sacrificing everyday usability. It was part of the GMTT1XX generation, a platform known for its robust construction and focus on work-truck functionality combined with increasing levels of refinement.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Double Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) Automatic |
| Start of production | 2020 year |
| End of production | 2023 year |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Petrol (Gasoline) |
| Weight-to-power ratio | 7.4 kg/Hp, 135.2 Hp/tonne |
| Weight-to-torque ratio | 4.7 kg/Nm, 212 Nm/tonne |
| Power | 401 Hp @ 5200 rpm |
| Torque | 629 Nm @ 4000 rpm, 463.93 lb.-ft. @ 4000 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | L8T |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 103.25 mm, 4.06 in. |
| Piston Stroke | 98 mm, 3.86 in. |
| Compression ratio | 10.8:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Direct injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | OHV, VVT |
| Engine oil capacity | 7.6 l, 8.03 US qt | 6.69 UK qt |
| Coolant | 14.6 l, 15.43 US qt | 12.85 UK qt |
| Kerb Weight | 2967 kg, 6541.12 lbs. |
| Max. weight | 4627 kg, 10200.79 lbs. |
| Max load | 1660 kg, 3659.67 lbs. |
| Fuel tank capacity | 136 l, 35.93 US gal | 29.92 UK gal |
| Permitted trailer load with brakes (12%) | 6577 kg, 14499.8 lbs. |
| Length | 6514 mm, 256.46 in. |
| Width including mirrors | 2079 mm, 81.85 in. |
| Height | 2027 mm, 79.8 in. |
| Wheelbase | 4127 mm, 162.48 in. |
| Front track | 1731 mm, 68.15 in. |
| Rear (Back) track | 1736 mm, 68.35 in. |
| Ride height (ground clearance) | 258 mm, 10.16 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 | 6 gears, automatic transmission Hydra-Matic |
| Front suspension | Coil spring, Double wishbone, Transverse stabilizer |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 355×40 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; 275/70 R18 |
| Wheel rims size | 7.5J x 17; 8J x 18 |
Powertrain & Engine Architecture
At the heart of the Sierra 2500HD is the 6.6-liter L8T V8 gasoline engine. This engine is a naturally aspirated, overhead valve (OHV) design featuring variable valve timing (VVT). Direct fuel injection is employed to optimize combustion efficiency and power output. The engine produces 401 horsepower at 5200 rpm and 464 lb-ft of torque at 4000 rpm. The engine’s robust internal components are designed for heavy-duty use, ensuring longevity under demanding conditions. The engine is paired with a six-speed Hydra-Matic automatic transmission, chosen for its durability and ability to handle the engine’s substantial torque. This transmission is calibrated for smooth shifts and responsive acceleration, even when towing heavy loads.
Driving Characteristics
The 6.6L V8 and six-speed automatic combination delivers a confident driving experience. While not as quick as some lighter-duty pickups, the Sierra 2500HD provides ample power for accelerating from a standstill and maintaining highway speeds, even when fully loaded. The automatic transmission’s gear ratios are optimized for towing, providing strong low-end torque. Compared to diesel variants, this gasoline engine offers a more responsive feel and a quieter cabin experience. However, it generally exhibits lower fuel economy, especially under heavy load. The long bed and double cab configuration contribute to a comfortable ride, but the truck’s size requires careful maneuvering in tight spaces.
Equipment & Trim Levels
The Sierra 2500HD Double Cab Long Bed with the 6.6L V8 was typically offered in SLE, Elevation, and Denali trim levels. The SLE trim served as the entry point, featuring standard amenities like a touchscreen infotainment system, Apple CarPlay and Android Auto compatibility, and a rearview camera. The Elevation trim added a more aggressive exterior appearance with blacked-out accents and upgraded interior materials. The Denali trim represented the pinnacle of luxury, offering premium leather upholstery, a Bose sound system, and advanced safety features. Optional extras included a power sunroof, heated and ventilated front seats, and a navigation system.
Chassis & Braking
The Sierra 2500HD utilizes a body-on-frame construction, providing a solid foundation for heavy-duty applications. The front suspension consists of coil springs and a double wishbone setup with a transverse stabilizer bar. The rear suspension employs a traditional leaf spring design, optimized for load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, with larger rotors at the front (355×40 mm) compared to the rear (360×34 mm). An Anti-lock Braking System (ABS) is standard. The steering system is a hydraulic rack-and-pinion setup, providing responsive and predictable handling.
Market Reception & Comparison
Critics generally praised the Sierra 2500HD’s robust construction, powerful engine, and comfortable ride. The 6.6L V8 was seen as a capable alternative to the diesel engines, particularly for buyers who prioritize responsiveness and a quieter cabin. However, fuel economy was a common concern, with the gasoline engine typically consuming more fuel than its diesel counterpart. Compared to the 6.6L Duramax diesel, the V8 offered less towing capacity and lower fuel efficiency, but at a lower initial cost. The gasoline engine was often favored by those who did not require the maximum towing capacity and preferred the simpler maintenance of a gasoline engine.
Legacy
The GMTT1XX Sierra 2500HD with the 6.6L V8 has proven to be a reliable and durable truck in the used car market. The L8T engine is known for its longevity, provided it receives regular maintenance. Common issues are relatively minor, often related to sensors or cooling system components. These trucks continue to be popular among buyers seeking a capable and affordable heavy-duty pickup. The combination of a powerful gasoline engine, a comfortable cabin, and a robust chassis makes this variant a compelling option for those needing a workhorse truck that can also handle daily driving duties. Its continued presence in the used market is a testament to its overall quality and dependability.
