The GMC Sierra 2500HD V (GMTT1XX) Double Cab Standard 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 sweet spot in the Sierra 2500HD lineup, balancing substantial capability with a degree of everyday usability. It was positioned as a robust work truck, appealing to owners needing serious towing and hauling capacity, but also desiring the comfort of a double cab and the convenience of an automatic transmission. This generation Sierra 2500HD, built on the GMTT1XX platform, aimed to improve upon its predecessors with enhanced technology, increased refinement, and continued durability.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX) Double Cab Standard 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 | 7.6 kg/Hp, 131.5 Hp/tonne |
| Weight-to-torque ratio | 4.8 kg/Nm, 206.2 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 | 3050 kg (6724.1 lbs) |
| Max. weight | 4695 kg (10350.7 lbs) |
| Max load | 1645 kg (3626.6 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 | 6107 mm (240.43 in) |
| Width including mirrors | 2079 mm (81.85 in) |
| Height | 2031 mm (79.96 in) |
| Wheelbase | 3795 mm (149.41 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). ICE drives rear wheels, front wheels engaged via clutch. |
| 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
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 direct fuel injection and variable valve timing (VVT). The L8T is a robust engine known for its durability and relatively simple design, eschewing forced induction in favor of a large displacement and high torque output. The direct injection system contributes to improved fuel efficiency and power delivery. The Hydra-Matic 6-speed automatic transmission is paired with this engine, providing smooth and reliable shifting. This transmission is designed to handle the high torque output of the 6.6L V8 and offers a balance between performance and fuel economy. The transmission features electronically controlled shifting and tow/haul mode for optimized performance when towing heavy loads.
Driving Characteristics
The 401 horsepower and 464 lb-ft of torque delivered by the 6.6L V8, coupled with the 6-speed automatic, provide a confident and capable driving experience. While not as quick as some of the diesel-powered Sierra 2500HD models, this gasoline variant offers ample power for everyday driving and towing. The automatic transmission is well-tuned, providing smooth gear changes and responsive acceleration. The gear ratios are optimized for towing, allowing the truck to maintain speed and control even when hauling heavy loads. Compared to the manual transmission options, the automatic provides greater convenience, especially in stop-and-go traffic. However, it may result in a slight reduction in fuel economy. The overall driving experience is characterized by a comfortable ride and a sense of solidity, typical of heavy-duty trucks.
Equipment & Trim Levels
The Double Cab Standard Bed configuration offered a good balance of passenger space and cargo capacity. Standard equipment typically included air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, 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 sunroof, navigation system, and various towing packages. The interior design was functional and durable, with a focus on practicality rather than luxury. The Standard Bed provided a useful cargo area for hauling materials and equipment.
Chassis & Braking
The Sierra 2500HD features a robust chassis designed to withstand the stresses of heavy-duty use. The front suspension utilizes a coil spring, double wishbone setup with a transverse stabilizer bar, while the rear suspension employs a traditional leaf spring configuration. This setup provides a comfortable ride and excellent load-carrying capacity. The braking system consists of ventilated discs on all four wheels, providing ample stopping power. Anti-lock brakes (ABS) are standard, enhancing safety and control. The truck’s solid rear axle contributes to its durability and towing capability. Steering is handled by a hydraulic power steering system, providing a responsive and precise feel.
Market Reception & Comparison
The GMC Sierra 2500HD with the 6.6L V8 and automatic transmission received generally positive reviews. Critics praised its powerful engine, comfortable ride, and capable towing performance. However, some noted that the fuel economy was not as good as some of the diesel-powered alternatives. Compared to the Duramax diesel engine, the gasoline V8 offered a lower initial cost but higher fuel consumption. The gasoline engine was also considered to be less refined and quieter than the diesel. Against competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD held its own, offering a compelling combination of capability, comfort, and value.
Legacy
The 6.6L L8T V8 paired with the Hydra-Matic automatic transmission has proven to be a reliable and durable powertrain. While not as fuel-efficient as diesel options, it remains a popular choice for owners who prioritize simplicity and affordability. In the used car market, these Sierra 2500HD models are generally well-regarded for their dependability and towing capacity. Regular maintenance, including oil changes and fluid checks, is crucial for ensuring the long-term health of this powertrain. The GMTT1XX platform Sierra 2500HD represents a solid and capable heavy-duty truck that continues to provide years of reliable service.
