The GMC Sierra 2500HD V (GMTT1XX) Double Cab Long Bed, equipped with the 6.6-liter V8 engine producing 401 horsepower, represents GMC’s entry into the heavy-duty pickup truck segment for the 2020-2023 model years. This configuration, featuring a four-wheel-drive system and an automatic transmission, was positioned as a robust work truck capable of significant towing and hauling, appealing to buyers needing substantial capability without necessarily opting for the highest trim levels. It falls within the fourth generation of the Sierra HD series, building upon the GMTT1XX platform which introduced significant updates to chassis, interior, and technology.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Double Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) 4WD 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 | 7.7 kg/Hp, 129.4 Hp/tonne |
| Weight-to-torque ratio | 4.9 kg/Nm, 203 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 | 3098 kg / 6829.92 lbs |
| Max. weight | 4763 kg / 10500.62 lbs |
| Max load | 1665 kg / 3670.7 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 permanently, and the front wheels are driven through an electrically or mechanically operated clutch if necessary. |
| Drive wheel | All wheel drive (4×4) |
| 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
The heart of this 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 Hydra-Matic 6-speed automatic transmission is the sole transmission option for this configuration. This transmission is known for its durability and ability to handle the high torque output of the 6.6L V8. The transmission’s gear ratios are tuned for both towing and everyday driving, providing a balance between power delivery and fuel efficiency.
Driving Characteristics
The 6.6L V8 and 6-speed automatic combination delivers a robust driving experience. While not as quick as lighter-duty trucks, the Sierra 2500HD provides ample power for accelerating with a load or tackling steep inclines. The automatic transmission shifts smoothly, and the torque converter multiplies engine torque for strong low-end acceleration. Compared to a manual transmission equipped Sierra 2500HD, the automatic offers greater convenience, especially in stop-and-go traffic or when towing. However, it may result in a slight reduction in fuel economy. The 4WD system provides enhanced traction in challenging conditions, making it suitable for off-road use and inclement weather.
Equipment & Trim Levels
The 6.6L V8 automatic configuration was available across several trim levels, including SLE, Elevation, and AT4. Standard features typically included air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, and a rearview camera. Higher trim levels added features such as leather upholstery, heated and ventilated front seats, a premium sound system, and advanced safety technologies like blind-spot monitoring and rear cross-traffic alert. Optional extras included a sunroof, navigation system, and various towing packages.
Chassis & Braking
The Sierra 2500HD utilizes a body-on-frame construction, providing a solid and durable platform for heavy-duty use. 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. 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 robust chassis and braking system are designed to handle the truck’s substantial weight and towing capacity.
Market Reception & Comparison
The GMC Sierra 2500HD with the 6.6L V8 and automatic transmission was generally well-received by critics and consumers. It was praised for its powerful engine, comfortable ride, and capable towing performance. Compared to the diesel-powered variants, the gasoline engine offered a lower initial cost but typically resulted in lower fuel economy, especially when towing. The automatic transmission was favored by many for its ease of use, while some enthusiasts preferred the control offered by a manual transmission. Against competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD held its own, offering a compelling combination of power, comfort, and capability.
Legacy
The L8T 6.6L V8 engine paired with the Hydra-Matic transmission has proven to be a relatively reliable powertrain. While some owners have reported minor issues with the fuel system or cooling system, major mechanical failures are uncommon. In the used car market, these Sierra 2500HD models remain popular choices for buyers seeking a capable and durable heavy-duty truck. Their relatively lower price point compared to diesel models makes them an attractive option for those who don’t require the ultimate in towing capacity or fuel efficiency. The GMTT1XX platform, and this powertrain combination, represent a significant step forward in GMC’s heavy-duty truck offerings, providing a blend of power, technology, and comfort.
