The GMC Sierra 2500HD V (GMTT1XX, facelift 2024) Crew Cab Long Bed, equipped with the 6.6-liter V8 engine producing 401 horsepower and paired with a 4WD automatic transmission, represents GMC’s offering in the heavy-duty pickup truck segment. Introduced with the GMTT1XX platform refresh in 2023, this variant builds upon the established Sierra 2500HD lineage, aiming to provide a balance of robust capability, towing capacity, and interior comfort. It slots into the lineup as a powerful, all-around work truck, positioned above the lower-trim diesel options and below the more luxurious Denali trims.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX, facelift 2024) Crew Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) 4WD 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 | 8 kg/Hp, 125.5 Hp/tonne |
| Weight-to-torque ratio | 5.1 kg/Nm, 196.8 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 | 3196 kg (7045.97 lbs) |
| Max. weight | 4831 kg (10650.53 lbs) |
| Max load | 1635 kg (3604.56 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 | 6776 mm (266.77 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 | 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 | 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
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. The direct injection system contributes to improved fuel efficiency and power output compared to traditional port fuel injection. 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. The engine is mated to a 10-speed Allison automatic transmission, known for its smooth shifting and ability to handle high torque loads. This transmission is crucial for maximizing the engine’s power and providing a comfortable driving experience, even when towing or hauling heavy loads.
Driving Characteristics
The 6.6L V8 and 10-speed automatic combination delivers a confident and capable driving experience. While not as fuel-efficient as the diesel options, the gasoline engine provides a more familiar power delivery and sound. The 10-speed transmission allows the engine to stay within its optimal power band, providing strong acceleration and responsive performance. The gear ratios are optimized for both towing and everyday driving. Compared to the 6.6L Duramax diesel, this gasoline variant offers quicker acceleration at lower weights but lacks the diesel’s superior torque for extremely heavy towing. The automatic transmission shifts smoothly and efficiently, minimizing gear hunting and providing a comfortable ride.
Equipment & Trim Levels
The Crew Cab Long Bed configuration offers ample space for passengers and cargo. Standard features typically include air conditioning, power windows and locks, a touchscreen infotainment system with Apple CarPlay and Android Auto compatibility, and a rearview camera. Higher trim levels add 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 often include a power sunroof, a navigation system, and various towing packages. The interior design focuses on functionality and durability, with materials chosen to withstand the demands of heavy-duty use.
Chassis & Braking
The Sierra 2500HD utilizes a robust chassis designed to handle heavy loads and demanding conditions. The front suspension features an independent torsion bar setup with double wishbones, providing a comfortable ride and good handling. 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 cone worm with recirculation balls, providing precise and responsive steering control.
Market Reception & Comparison
The GMC Sierra 2500HD with the 6.6L V8 and automatic transmission received generally positive reviews, particularly for its strong performance and comfortable ride. Critics noted that while the diesel engine offered superior towing capacity, the gasoline engine provided a more accessible entry point into the heavy-duty truck segment. Fuel economy was a common point of comparison, with the diesel models consistently outperforming the gasoline variant in this area. Reliability ratings have been generally good, with owners reporting few major issues. 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 6.6L L8T V8 and 10-speed Allison automatic transmission combination has proven to be a reliable and durable powertrain. While the diesel variants remain popular for their towing prowess, the gasoline engine continues to appeal to buyers who prioritize performance and a lower initial cost. In the used car market, these Sierra 2500HD models are generally well-regarded for their build quality and longevity. Regular maintenance, including oil changes and transmission fluid flushes, is crucial for ensuring the long-term reliability of this powertrain. The GMTT1XX platform, and this specific configuration, represents a significant step forward in heavy-duty truck technology, offering a blend of capability, comfort, and efficiency.
