The GMC Sierra 3500HD III, specifically the Extended Cab Long Box configuration with the 6.0-liter V8 engine producing 360 horsepower, represents a significant iteration in GMC’s heavy-duty truck lineage. Produced from 2007 through 2010 (GMT900 platform), this variant was aimed at buyers needing substantial towing and hauling capacity without sacrificing some degree of interior space and comfort. It occupied a middle ground within the 3500HD lineup, offering a balance between the more utilitarian standard cab models and the more luxurious crew cab versions. This truck was a mainstay of the American work truck market, designed for demanding jobs and long hours.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD III (GMT900) Extended Cab Long Box |
| Type (Engine) | 6.0 V8 (360 Hp) SRW Automatic |
| Start of production | 2007 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 2 |
| Fuel Type | Petrol (Gasoline) |
| Weight-to-power ratio | 7.4 kg/Hp, 134.6 Hp/tonne |
| Weight-to-torque ratio | 5.2 kg/Nm, 192.6 Nm/tonne |
| Power | 360 Hp @ 5400 rpm |
| Power per litre | 60.3 Hp/l |
| Torque | 515 Nm @ 4200 rpm, 379.84 lb.-ft. @ 4200 rpm |
| Maximum engine speed | 6000 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Vortec LY6 |
| Engine displacement | 5967 cm3, 364.13 cu. in. |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 101.6 mm, 4 in. |
| Piston Stroke | 92 mm, 3.62 in. |
| Compression ratio | 9.6:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | OHV |
| Engine oil capacity | 5.7 l, 6.02 US qt | 5.02 UK qt |
| Coolant | 15.5 l, 16.38 US qt | 13.64 UK qt |
| Kerb Weight | 2674 kg, 5895.16 lbs |
| Max. weight | 4400 kg, 9700.34 lbs |
| Max load | 1726 kg, 3805.18 lbs |
| Trunk (boot) space – maximum | 2170 l, 76.63 cu. ft |
| Fuel tank capacity | 129 l, 34.08 US gal | 28.38 UK gal |
| Permitted trailer load with brakes (12%) | 5624 kg, 12398.8 lbs |
| Length | 6330 mm, 249.21 in |
| Width including mirrors | 2436 mm, 95.91 in |
| Height | 1931 mm, 76.02 in |
| Wheelbase | 4001 mm, 157.52 in |
| Front track | 1742 mm, 68.58 in |
| Rear (Back) track | 1676 mm, 65.98 in |
| Ride height (ground clearance) | 233 mm, 9.17 in |
| Minimum turning circle (turning diameter) | 16 m, 52.49 ft |
| 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 | Independent torsion bar, double wishbone |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 325×38 mm |
| Rear brakes | Ventilated discs, 325×30 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 265/75 R16; 265/70 R17; 225/75 R17 |
| Wheel rims size | 6.5J x 17; 7J x 16; 7.5J x 17 |
Powertrain & Engine Architecture
At the heart of this Sierra 3500HD variant lies the Vortec LY6 6.0-liter V8 engine. This engine is a member of the Vortec family, known for its robust construction and relatively simple design. The LY6 utilizes a cast iron block and aluminum cylinder heads, contributing to its durability. It features a 9.6:1 compression ratio and is equipped with a multi-port fuel injection system, delivering fuel directly to each cylinder. The overhead valve (OHV) valvetrain, while not as technologically advanced as overhead cam designs, is known for its reliability and ease of maintenance. The engine produces 360 horsepower at 5400 rpm and 515 Nm (379.84 lb-ft) of torque at 4200 rpm. This torque output is crucial for heavy towing and hauling. The engine is mated to a 6-speed Hydra-Matic automatic transmission, designed to handle the substantial power and torque. This transmission provides smooth shifting and adequate gear ratios for both on-road driving and demanding work applications.
Driving Characteristics
The 6.0L V8 and 6-speed automatic combination in the Sierra 3500HD delivers a driving experience focused on capability rather than outright speed. Acceleration is adequate for a vehicle of this size and weight, but the emphasis is on providing strong low-end torque for towing and hauling. The automatic transmission is well-tuned for this purpose, offering relatively quick downshifts when needed and maintaining a comfortable cruising speed on the highway. Compared to the available Duramax diesel engine, the 6.0L V8 offers less torque but is significantly less expensive to purchase and maintain. Compared to the 4.8L V8, the 6.0L provides a noticeable increase in power and towing capacity. The extended cab configuration provides additional interior space compared to the standard cab, making it more comfortable for passengers on longer trips.
Equipment & Trim Levels
The Sierra 3500HD Extended Cab Long Box with the 6.0L V8 typically came standard with features like air conditioning, power windows and locks, and a basic audio system. The interior typically featured cloth upholstery and a functional, durable dashboard layout. Optional extras included leather upholstery, a premium audio system, power-adjustable seats, and a navigation system. Trim levels varied, but generally offered increasing levels of comfort and convenience features. The extended cab provided a small rear seating area, suitable for occasional passengers or cargo.
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 and good handling. The rear suspension employs a traditional leaf spring design, optimized for load-carrying capacity. Braking duties are handled by ventilated discs on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) is standard, enhancing safety during emergency braking situations. The truck’s heavy-duty frame and suspension components contribute to its impressive towing and hauling capabilities.
Market Reception & Comparison
The GMC Sierra 3500HD with the 6.0L V8 engine was generally well-received by critics and consumers alike. It was praised for its strong towing capacity, comfortable ride, and relatively affordable price compared to diesel-powered alternatives. Fuel economy, however, was a common criticism, as the 6.0L V8 is not particularly fuel-efficient. Reliability was generally good, although some owners reported issues with the active fuel management system (which deactivated cylinders to improve fuel economy). Compared to the Duramax diesel, the 6.0L V8 offered a lower initial cost and simpler maintenance, but at the expense of fuel economy and ultimate towing capacity.
Legacy
The GMT900 generation Sierra 3500HD, and specifically the 6.0L V8/automatic combination, remains a popular choice in the used truck market today. Its robust construction and proven powertrain make it a reliable workhorse for those needing a heavy-duty truck. While newer trucks offer more advanced features and improved fuel economy, the GMT900 Sierra 3500HD represents a solid value for buyers seeking a capable and affordable truck. The LY6 engine, while not without its quirks, is generally considered a durable and relatively easy-to-maintain powerplant, contributing to the long-term appeal of this truck.
