The GMC Sierra 2500HD, in its fifth generation (GMTT1XX), underwent a significant refresh for the 2024 model year. This article focuses specifically on the Double Cab Long Bed configuration equipped with the 6.6-liter V8 gasoline engine producing 401 horsepower, paired with a 10-speed automatic transmission. Introduced in 2023 with the facelift, this variant represents a balance between capability and everyday usability within the Sierra 2500HD lineup, targeting buyers needing substantial towing and hauling capacity without the diesel’s higher price point. It serves as a workhorse for those prioritizing gasoline power and a more conventional ownership experience.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX, facelift 2024) Double Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) Automatic |
| Start of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Petrol (Gasoline) |
| Weight-to-power ratio | 7.5 kg/Hp, 132.9 Hp/tonne |
| Weight-to-torque ratio | 4.8 kg/Nm, 208.4 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 |
| 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 | 3018 kg (6653.55 lbs.) |
| Max. weight | 4627 kg (10200.79 lbs.) |
| Max load | 1609 kg (3547.24 lbs.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 7257 kg (15998.95 lbs.) |
| Length | 6534 mm (257.24 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) | 257 mm (10.12 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine (ICE) |
| Number of gears and type of gearbox | 10 gears, automatic transmission Allison |
| Front suspension | Independent torsion bar, double wishbone |
| 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 | 245/75 R17; 265/70 R17; 275/70 R18; 275/65 R20 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 20 |
Powertrain & Engine Architecture
The heart of this Sierra 2500HD variant is the 6.6-liter L8T V8 gasoline engine. This engine utilizes a traditional overhead valve (OHV) valvetrain and direct fuel injection to maximize efficiency and power output. The direct injection system allows for precise fuel delivery, contributing to improved combustion and reduced emissions. The engine produces 401 horsepower at 5200 rpm and 629 Nm (463.93 lb-ft) of torque at 4000 rpm. The engine’s robust construction is designed for heavy-duty applications, prioritizing durability and longevity. Paired with this engine is the Allison 10-speed automatic transmission. This transmission is known for its smooth shifting and ability to handle high torque loads, crucial for towing and hauling. The 10-speed configuration provides a wide gear ratio spread, optimizing both fuel economy and performance.
Driving Characteristics
The 6.6L V8 and 10-speed automatic combination delivers a confident driving experience. While not as fuel-efficient as the diesel options, the gasoline engine provides a more familiar driving feel for many American truck buyers. Acceleration is brisk, especially considering the vehicle’s weight, and the 10-speed transmission keeps the engine in its optimal power band. The gear ratios are well-spaced, providing ample torque for towing and hauling, while also allowing for comfortable highway cruising. Compared to the 6.6L Duramax diesel, this gasoline variant offers less low-end torque, requiring slightly more throttle input when heavily loaded. However, it responds more readily to throttle changes and offers a more linear power delivery. The gasoline engine is also quieter and smoother than the diesel, contributing to a more refined driving experience.
Equipment & Trim Levels
The 2500HD Double Cab Long Bed with the 6.6L V8 typically falls into the mid-range of the Sierra 2500HD trim levels. Standard features generally include air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, and a rearview camera. Interior upholstery is typically cloth, with options for leather upgrades on higher trims. The Double Cab configuration provides comfortable seating for five passengers. Available options include a premium audio system, navigation, heated and ventilated front seats, and a variety of driver-assistance features such as lane departure warning and automatic emergency braking. The Long Bed configuration provides ample cargo space for hauling equipment and materials.
Chassis & Braking
The Sierra 2500HD utilizes a body-on-frame construction, providing a robust and durable platform for heavy-duty applications. The front suspension features an independent torsion bar setup with double wishbones, offering a comfortable ride and good handling characteristics. 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 utilizes a hydraulic power steering setup, providing a responsive and predictable steering feel.
Market Reception & Comparison
Critics generally praised the Sierra 2500HD’s overall capability and refinement. The 6.6L V8 engine was seen as a viable alternative to the diesel, particularly for buyers who prioritize a lower initial cost and a more familiar driving experience. Fuel economy, however, was a common criticism, as the gasoline engine typically delivers lower MPG figures compared to the diesel. Compared to the diesel variants, the 6.6L V8 offers a lower price point and simpler maintenance requirements. However, it lacks the diesel’s superior towing capacity and fuel efficiency. The gasoline engine is also generally considered to be more reliable than the diesel, with fewer potential issues related to emissions control systems.
Legacy
The 6.6L L8T V8 engine has proven to be a reliable and durable powertrain in the Sierra 2500HD. While not as popular as the Duramax diesel, it has earned a reputation for its longevity and relatively low maintenance costs. In the used car market, these models represent a good value for buyers seeking a capable and dependable heavy-duty truck. The Allison 10-speed automatic transmission has also proven to be a robust and reliable component, contributing to the overall longevity of the powertrain. As these trucks age, proper maintenance and regular servicing are crucial to ensure continued reliability and performance.
