The GMC Sierra 3500HD, specifically the V (GMTT1XX) 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 from the 2020 to 2023 model years. This variant occupied a significant position within the Sierra 3500HD lineup, catering to buyers needing substantial towing and payload capacity without sacrificing everyday usability. It was positioned as a robust work truck, appealing to those requiring a powerful and capable vehicle for both commercial and personal applications. The GMTT1XX platform, introduced in 2020, brought significant updates to the Sierra HD series, focusing on increased capability, improved technology, and enhanced interior refinement.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX) Double Cab Long Bed |
| Type (Engine) | 6.6 V8 (401 Hp) 4WD 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 | 7.9 kg/Hp, 126.8 Hp/tonne |
| Weight-to-torque ratio | 5 kg/Nm, 198.9 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 | 3162 kg (6971.02 lbs) |
| Max. weight | 5171 kg (11400.1 lbs) |
| Max load | 2009 kg (4429.09 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) | 264 mm (10.39 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 | 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 3500HD 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 produces 401 horsepower at 5200 rpm and 464 lb-ft of torque at 4000 rpm. The direct injection system optimizes combustion efficiency and power delivery. The engine’s robust internal components are designed for heavy-duty use, ensuring longevity and reliability under demanding conditions. The engine is longitudinally mounted in the chassis. Power is transmitted to all four wheels through a six-speed Hydra-Matic automatic transmission, known for its durability and smooth shifting characteristics. This transmission is electronically controlled, adapting shift points based on driving conditions and throttle input.
Driving Characteristics
The 6.6L V8 and six-speed automatic combination delivers a balance of power and usability. While not as quick as some lighter-duty pickups, the Sierra 3500HD provides ample torque for towing and hauling heavy loads. The automatic transmission is well-tuned for this application, offering smooth and predictable shifts. The gear ratios are optimized for maximizing towing capacity and providing sufficient power in various driving scenarios. Compared to a diesel-powered Sierra 3500HD, this gasoline variant offers a more responsive feel at lower engine speeds, but lacks the diesel’s exceptional low-end torque and fuel efficiency. The 4WD system provides enhanced traction in challenging conditions, making it suitable for both on-road and off-road use.
Equipment & Trim Levels
The Double Cab Long Bed configuration offered a spacious cabin with seating for five passengers. Standard features 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 focused on functionality and durability, with materials chosen to withstand heavy use. The Double Cab configuration provided ample rear-seat legroom, making it comfortable for passengers on long journeys.
Chassis & Braking
The Sierra 3500HD features a fully boxed frame designed for maximum strength and rigidity. The front suspension utilizes a coil spring, double wishbone setup with a transverse stabilizer bar, providing a comfortable ride and precise handling. The rear suspension employs a rigid axle with leaf springs, optimized for carrying heavy loads. The braking system consists of ventilated discs on all four wheels, providing ample stopping power. The front brakes measure 355×40 mm, while the rear brakes are 360×34 mm. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. The steering system is a cone worm with recirculation balls, providing a responsive and precise steering feel.
Market Reception & Comparison
The GMC Sierra 3500HD with the 6.6L V8 and automatic transmission received generally positive reviews. Critics praised its robust construction, ample towing capacity, and comfortable ride. However, some noted that the gasoline engine’s fuel economy was lower compared to the available diesel options. Compared to the Duramax diesel engine, the gasoline V8 offered a lower initial cost but higher operating expenses due to fuel consumption. The gasoline engine was often favored by buyers who did not require the extreme towing capacity of the diesel and preferred a more responsive driving experience. Reliability reports generally indicated good long-term durability for the powertrain, although regular maintenance was crucial for optimal performance.
Legacy
The 2020-2023 GMC Sierra 3500HD with the 6.6L V8 and automatic transmission remains a popular choice in the used truck market. Its robust construction and proven powertrain contribute to its long-term reliability. While the diesel variants often command a higher resale value, the gasoline V8 offers a more affordable entry point into the heavy-duty truck segment. These trucks are often sought after by individuals and businesses needing a capable and dependable workhorse for towing, hauling, and general-purpose use. The GMTT1XX platform’s improvements in technology and refinement have helped maintain the Sierra 3500HD’s position as a competitive offering in the heavy-duty truck market.
