The GMC Sierra 3500HD, specifically the 2024 model year facelift in Double Cab Long Bed configuration with the 6.6-liter V8 engine producing 401 horsepower, represents GMC’s heavy-duty full-size pickup truck offering. Introduced as part of the GMTT1XX generation, this variant caters to buyers needing substantial towing and payload capacity without sacrificing everyday usability. The 2024 refresh brought updated styling, enhanced technology, and refinements to the already capable platform. This particular configuration, combining the powerful V8 with a four-wheel drive system and an automatic transmission, positions itself as a workhorse capable of handling demanding tasks while providing a relatively comfortable driving experience.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX, facelift 2024) Double Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) 4WD SRW Automatic |
| Start of production | 2024 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Petrol (Gasoline) |
| Weight-to-power ratio | 8 kg/Hp, 124.4 Hp/tonne |
| Weight-to-torque ratio | 5.1 kg/Nm, 195.2 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 |
| 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 | 3223 kg (7105.5 lbs) |
| Max. weight | 5261 kg (11598.52 lbs) |
| Max load | 2038 kg (4493.02 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 | 2054 mm (80.87 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 | 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 | 275/70 R18; 275/65 R20 |
| Wheel rims size | 8J x 18; 8.5J x 20 |
Powertrain & Engine Architecture
At the heart of the 2024 Sierra 3500HD is 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 allows for precise fuel delivery, contributing to improved efficiency and power output. 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 and large displacement are geared towards providing substantial low-end torque, crucial for heavy towing and hauling. The engine is paired with a heavy-duty 10-speed Allison automatic transmission. This transmission is known for its durability and smooth shifting, optimized for managing the engine’s power and the truck’s substantial weight. The Allison transmission features electronically controlled shifting and tow/haul mode for enhanced performance when towing.
Driving Characteristics
The combination of the 6.6L V8 and the 10-speed Allison automatic delivers a driving experience focused on capability rather than outright speed. While not a sports truck, the Sierra 3500HD provides ample power for accelerating with a load or maintaining highway speeds. The 10-speed transmission helps keep the engine in its optimal power band, even when towing. Compared to lighter-duty Sierra 1500 models, the 3500HD feels more substantial and deliberate in its movements. Compared to a diesel variant of the 3500HD, the gasoline engine offers quicker throttle response and a quieter cabin experience, but sacrifices the diesel’s superior fuel economy and ultimate towing capacity. The four-wheel drive system provides enhanced traction in various conditions, making it suitable for both on-road and off-road use.
Equipment & Trim Levels
The 2024 Sierra 3500HD Double Cab Long Bed with the 6.6L V8 typically comes standard with a comprehensive suite of features. These 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, such as Denali, add premium features like leather upholstery, heated and ventilated seats, a premium sound system, and advanced safety technologies like adaptive cruise control and lane departure warning. Optional extras include a power sunroof, a bed liner, and various towing packages. Interior upholstery typically consists of cloth or vinyl in lower trims, with leather becoming standard on higher-end models. The dashboard layout is functional and driver-focused, with easy-to-reach controls.
Chassis & Braking
The Sierra 3500HD utilizes a robust chassis designed to withstand heavy loads. The front suspension features an independent torsion bar setup with double wishbones, providing a comfortable ride while maintaining stability. 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. Steering is accomplished via a hydraulic power steering system with a cone worm and recirculation balls mechanism. The truck’s substantial weight necessitates a robust braking system to ensure safe and controlled stopping power.
Market Reception & Comparison
The 2024 GMC Sierra 3500HD with the 6.6L V8 received generally positive reviews, particularly for its towing capacity and overall capability. Critics noted the engine’s ample power and the smooth operation of the 10-speed Allison transmission. Fuel economy, however, was a common point of criticism, as gasoline engines typically consume more fuel than their diesel counterparts. Compared to the Duramax diesel engine option, the 6.6L V8 offers a lower initial cost but higher long-term fuel expenses. The gasoline engine is often favored by buyers who prioritize lower upfront costs and a quieter cabin experience over maximum fuel efficiency and towing capacity.
Legacy
The GMTT1XX generation Sierra 3500HD, and specifically the 6.6L V8/Allison automatic combination, is expected to be a durable and reliable powertrain. The Allison transmission, in particular, has a strong reputation for longevity. While long-term reliability data is still emerging for the 2024 facelift, previous iterations of this engine and transmission have proven to be dependable. On the used car market, these trucks are likely to hold their value due to their capability and reputation for durability. Regular maintenance, including oil changes and transmission fluid flushes, will be crucial for ensuring the longevity of this powertrain.
