The GMC Sierra 3500HD, specifically the V (GMTT1XX) Double Cab Long Bed configuration powered by the 6.6-liter V8 engine producing 401 horsepower, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2020 through 2023, this variant aimed to provide a balance of capability, comfort, and technology for buyers needing substantial towing and hauling capacity. It slots into the Sierra 3500HD lineup as a robust, work-oriented option, positioned above the lighter-duty 1500 series and alongside other 3500HD configurations with varying engine and trim levels.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX) Double Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) SRW 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, 132.2 Hp/tonne |
| Weight-to-torque ratio | 4.8 kg/Nm, 207.3 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 | 3034 kg (6688.83 lbs) |
| Max. weight | 5035 kg (11100.27 lbs) |
| Max load | 2001 kg (4411.45 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 | 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) | 284 mm (11.18 in) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| 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 |
INTRODUCTION
The GMC Sierra 3500HD V (GMTT1XX) Double Cab Long Bed with the 6.6L V8 engine and automatic transmission, launched in 2020, represents the fourth generation of GMC’s heavy-duty pickup line. Built on the GMTT1XX platform, this truck was designed to offer increased capability, refined interior appointments, and advanced technology compared to its predecessors. The Double Cab configuration provides a larger rear seating area than the standard cab, making it suitable for both work crews and families. The long bed maximizes cargo space, catering to owners who frequently haul large items. This particular variant aimed to bridge the gap between the base engine options and the more powerful diesel offerings, providing a strong gasoline-powered alternative.
Powertrain & Engine Architecture
At the heart of this Sierra 3500HD lies the L8T 6.6-liter naturally aspirated V8 engine. This engine utilizes direct fuel injection, a feature that improves efficiency and power output. The engine also incorporates variable valve timing (VVT) to optimize performance across the rev range. 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 contribute to its ability to handle heavy loads. The engine is paired with a six-speed Hydra-Matic automatic transmission, chosen for its durability and smooth shifting characteristics. This transmission is specifically calibrated to work with the engine’s torque curve, providing adequate power delivery for towing and hauling.
Driving Characteristics
The 6.6L V8 and six-speed automatic combination delivers a capable, if not overly sporty, driving experience. While not as quick as some of the lighter-duty pickups or those equipped with the diesel engine, the Sierra 3500HD provides ample power for everyday driving and demanding tasks. The automatic transmission shifts smoothly, and the gear ratios are well-suited for towing. The truck feels planted and stable, even when carrying a heavy load. Compared to manual transmission versions (which were less common in this configuration), the automatic offers greater convenience, especially in stop-and-go traffic. Compared to the diesel variants, this gasoline engine is noticeably quieter and offers quicker throttle response at lower RPMs, but lacks the diesel’s superior torque for extremely heavy towing.
Equipment & Trim Levels
The Sierra 3500HD Double Cab Long Bed with the 6.6L V8 typically came standard with features like air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, and a rearview camera. Higher trim levels, such as SLE and Denali, added features like leather upholstery, heated and ventilated seats, a premium sound system, and advanced safety technologies like lane departure warning and automatic emergency braking. Optional extras included a sunroof, navigation system, and a variety of towing packages. The interior design focused on functionality and durability, with comfortable seating and easy-to-use controls.
Chassis & Braking
The Sierra 3500HD features a robust chassis designed to withstand heavy loads. The front suspension utilizes coil springs and a double wishbone setup, while the rear suspension employs a traditional leaf spring design. This configuration provides a comfortable ride while maintaining excellent load-carrying capacity. The truck is equipped with ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) is standard. The rear axle is a solid axle, contributing to the truck’s durability and towing capability. Steering is handled by a hydraulic power steering system, offering a responsive and predictable feel.
Market Reception & Comparison
Critics generally praised the Sierra 3500HD for its strong engine, comfortable ride, and spacious interior. The 6.6L V8 was seen as a good option for buyers who didn’t need the extreme towing capacity of the diesel engine but still wanted a powerful and capable truck. Fuel economy, however, was a common criticism, as the gasoline engine is less efficient than the diesel alternative. Compared to the Duramax diesel, the 6.6L V8 offered a lower initial cost but higher long-term fuel expenses. Reliability was generally good, with few major issues reported.
Legacy
The GMC Sierra 3500HD V (GMTT1XX) Double Cab Long Bed with the 6.6L V8 engine has established itself as a reliable and capable work truck in the used car market. The L8T engine is known for its durability, and the Hydra-Matic transmission is generally considered to be robust. While fuel economy may not be its strong suit, the truck’s overall value and capability make it a popular choice for buyers seeking a heavy-duty pickup. These trucks continue to be sought after by those needing a dependable vehicle for towing, hauling, and general work purposes, and well-maintained examples hold their value reasonably well.
