The GMC Sierra 2500HD V (GMTT1XX) Crew Cab Long Bed, equipped with the 6.6-liter V8 engine producing 401 horsepower and paired with a 4WD automatic transmission, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2020 to 2023, this variant occupied a sweet spot in the Sierra 2500HD lineup, balancing robust capability with a degree of everyday usability. It was part of the GMTT1XX generation, a substantial redesign of GMC’s heavy-duty trucks focused on increased towing capacity, improved interior refinement, and enhanced technology.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Crew Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 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 | Petrol (Gasoline) |
| Weight-to-power ratio | 7.8 kg/Hp, 127.7 Hp/tonne |
| Weight-to-torque ratio | 5 kg/Nm, 200.3 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 | 3140 kg / 6922.52 lbs. |
| Max. weight | 4831 kg / 10650.53 lbs. |
| Max load | 1691 kg / 3728.02 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 | 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). ICE drives rear wheels, front wheels engaged via clutch. |
| 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 this Sierra 2500HD variant lies the 6.6-liter L8T V8 gasoline engine. This engine is a naturally aspirated, overhead valve (OHV) design featuring variable valve timing (VVT). The L8T utilizes direct fuel injection, contributing to improved efficiency and power delivery. The engine’s robust construction is geared towards heavy-duty applications, prioritizing durability and longevity. The Hydra-Matic 6-speed automatic transmission is the sole transmission option for this configuration. This transmission is known for its smooth shifting and ability to handle the engine’s substantial torque output. The transmission is electronically controlled, adapting shift points based on driving conditions and throttle input.
Driving Characteristics
The 401 horsepower and 464 lb-ft of torque provided by the 6.6L V8 and 6-speed automatic combination deliver a capable driving experience. While not as quick as lighter-duty trucks, the Sierra 2500HD offers ample power for towing and hauling heavy loads. The automatic transmission is well-tuned for this application, providing smooth and predictable shifts. Compared to the available Duramax diesel engine, this gasoline variant offers a more responsive feel at lower RPMs, but lacks the diesel’s exceptional low-end torque and fuel efficiency. The gear ratios are optimized for towing, with lower gears providing strong pulling power, while higher gears allow for comfortable highway cruising.
Equipment & Trim Levels
The 2500HD Crew Cab Long Bed with the 6.6L V8 typically came standard with features like a touchscreen infotainment system, Apple CarPlay and Android Auto compatibility, and a rearview camera. Higher trim levels, such as the SLT and Denali, added features like leather upholstery, heated and ventilated seats, a premium sound system, and advanced safety technologies. Optional extras included a power sunroof, a navigation system, and a bed liner. The Crew Cab configuration provides ample space for passengers, making it a comfortable choice for families or work crews.
Chassis & Braking
The Sierra 2500HD features a fully boxed frame designed for strength and rigidity. The front suspension utilizes a coil spring, double wishbone setup with a transverse stabilizer bar, while the rear suspension employs a traditional leaf spring design. This configuration is optimized for handling heavy loads and providing a comfortable ride. Braking duties are handled by ventilated disc brakes at all four corners, providing ample stopping power. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. The truck’s robust chassis and braking system contribute to its impressive towing and payload capacities.
Market Reception & Comparison
Critics generally praised the Sierra 2500HD for its powerful engine, comfortable ride, and spacious interior. The 6.6L V8 was seen as a viable alternative to the Duramax diesel, particularly for buyers who didn’t require the diesel’s maximum towing capacity or fuel efficiency. However, the gasoline engine’s fuel economy was a common criticism, especially compared to the diesel option. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD offered a competitive combination of features, performance, and value.
Legacy
The GMTT1XX generation Sierra 2500HD, and specifically the 6.6L V8/automatic combination, has proven to be a relatively reliable powertrain. While the gasoline engine may require more frequent maintenance than the Duramax diesel, it is generally considered to be a durable and long-lasting engine. On the used car market, these trucks hold their value reasonably well, particularly those that have been well-maintained and haven’t been subjected to excessive heavy use. The combination of capability, comfort, and available features makes this variant a popular choice for buyers seeking a capable and versatile heavy-duty pickup truck.
