The GMC Sierra 3500HD III, produced from 2007 to 2010, represented the third generation of GMC’s heavy-duty full-size pickup truck line. This generation, designated GMT900, offered a significant upgrade in capability, refinement, and interior space compared to its predecessor. The Extended Cab Long Box configuration, paired with the 6.0-liter Vortec LY6 V8 engine producing 360 horsepower and coupled to a 6-speed Hydra-Matic automatic transmission, was a popular choice for buyers needing a robust work truck with a degree of everyday usability. This particular variant occupied a sweet spot in the lineup, offering a substantial increase in towing and hauling capacity over the lighter-duty Sierra 1500, while remaining more accessible than the diesel-powered 3500HD models.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD III (GMT900) Extended Cab Long Box |
| Type (Engine) | 6.0 V8 (360 Hp) 4WD 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 | 7.8 kg/Hp, 129 Hp/tonne |
| Weight-to-torque ratio | 5.4 kg/Nm, 184.5 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 | 2791 kg, 6153.1 lbs. |
| Max. weight | 4490 kg, 9898.76 lbs. |
| Max load | 1699 kg, 3745.65 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%) | 5488 kg, 12098.97 lbs. |
| Length | 6330 mm, 249.21 in. |
| Width including mirrors | 2436 mm, 95.91 in. |
| Height | 1927 mm, 75.87 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 | All wheel drive (4×4). Internal Combustion engine. 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. |
| 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
The heart of this Sierra 3500HD variant is the 6.0-liter Vortec LY6 V8 engine. This engine is a member of the Vortec family, known for its robust construction and relatively simple design. The LY6 features a cast iron block and aluminum cylinder heads, contributing to its durability. It utilizes a traditional overhead valve (OHV) valvetrain with two valves per cylinder. Fuel delivery is managed by a multi-port fuel injection system, providing precise fuel metering for optimal performance and efficiency. The 6.0L Vortec engine is known for its broad torque curve, making it well-suited for heavy-duty applications. The engine is mated to a 6-speed Hydra-Matic automatic transmission, a significant upgrade over the older 4-speed units. This transmission provides smoother shifts and improved fuel economy, while also offering the capability to handle the engine’s substantial torque output. The 6-speed configuration also allows for a wider range of gear ratios, optimizing performance for both towing and everyday driving.
Driving Characteristics
The 6.0-liter V8 and 6-speed automatic combination in the Sierra 3500HD delivers a capable and confident driving experience. While not as quick as some of the lighter-duty pickups, the 360 horsepower and 380 lb-ft of torque provide ample power for hauling heavy loads and navigating challenging terrain. The automatic transmission is well-tuned, offering smooth and predictable shifts. Compared to the manual transmission options, the automatic prioritizes ease of use and convenience, making it a popular choice for drivers who frequently operate in stop-and-go traffic or tow heavy trailers. The gear ratios are optimized for towing, providing strong low-end torque and minimizing the need for frequent downshifts. However, the automatic transmission does slightly diminish fuel economy compared to the manual transmission versions.
Equipment & Trim Levels
The Sierra 3500HD offered a range of trim levels, with the 6.0-liter V8/automatic combination typically found in the WT (Work Truck), SLE, and SLT trims. Standard features on the WT trim included air conditioning, a basic audio system, and vinyl upholstery. The SLE trim added features such as power windows and locks, keyless entry, and an upgraded audio system. The SLT trim, the most luxurious option, included leather upholstery, heated seats, a premium audio system, and additional chrome exterior trim. Optional extras available across the trim levels included a navigation system, a sunroof, and a rear-seat entertainment system.
Chassis & Braking
The GMT900 Sierra 3500HD features a fully boxed frame, providing a solid foundation for its heavy-duty capabilities. The front suspension utilizes an independent torsion bar setup with double wishbone control arms, offering a comfortable ride and precise 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, providing ample stopping power even when towing heavy loads. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. The 4WD system utilizes an electronically controlled transfer case, allowing the driver to easily switch between two-wheel drive and four-wheel drive modes.
Market Reception & Comparison
The 6.0-liter V8-powered Sierra 3500HD was generally well-received by critics and consumers alike. It was praised for its strong towing capacity, comfortable ride, and refined interior. Compared to the diesel-powered 3500HD models, the 6.0-liter V8 offered a lower initial cost and simpler maintenance requirements. However, it lacked the diesel’s superior fuel economy and ultimate towing capacity. Compared to the Sierra 1500, the 3500HD provided a significant increase in payload and towing capacity, making it the preferred choice for those needing a truly heavy-duty truck. Fuel economy was typical for a vehicle of this size and capability, averaging around 14-16 mpg in combined driving.
Legacy
The GMT900 Sierra 3500HD, particularly the 6.0-liter V8/automatic combination, has proven to be a reliable and durable truck. The Vortec LY6 engine is known for its longevity, and the 6-speed Hydra-Matic transmission has also demonstrated good reliability. Today, these trucks are readily available on the used market at relatively affordable prices. They remain a popular choice for those needing a capable and dependable work truck. While maintenance costs may be higher than newer vehicles, the Sierra 3500HD’s robust construction and readily available parts supply ensure that it can continue to provide years of reliable service.
