The GMC Sierra 2500HD III, specifically the Extended Cab Long Box configuration with the 6.0-liter V8 engine and automatic transmission, was a prominent heavy-duty pickup truck produced by General Motors from 2007 to 2010. Falling within the GMT900 platform generation, this variant occupied a sweet spot in the Sierra 2500HD lineup, offering a balance between capability, comfort, and affordability. It was designed to cater to owners needing substantial towing and hauling capacity without the expense of the diesel-powered options, and served as a workhorse for both commercial and personal use in the North American market.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900) Extended Cab Long Box |
| Type (Engine) | 6.0 V8 (360 Hp) 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 | 7.2 kg/Hp, 138.8 Hp/tonne |
| Weight-to-torque ratio | 5 kg/Nm, 198.5 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 | 2594 kg, 5718.79 lbs. |
| Max. weight | 4173 kg, 9199.89 lbs. |
| Max load | 1579 kg, 3481.1 lbs. |
| Trunk (boot) space – maximum | 2138 l, 75.5 cu. ft. |
| Fuel tank capacity | 129 l, 34.08 US gal | 28.38 UK gal |
| Permitted trailer load with brakes (12%) | 5670 kg, 12500.21 lbs. |
| Length | 6330 mm, 249.21 in. |
| Width including mirrors | 2436 mm, 95.91 in. |
| Height | 1930 mm, 75.98 in. |
| Wheelbase | 4001 mm, 157.52 in. |
| Front track | 1744 mm, 68.66 in. |
| Rear (Back) track | 1676 mm, 65.98 in. |
| Ride height (ground clearance) | 243 mm, 9.57 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 | 245/75 R16; 265/75 R17 |
| Wheel rims size | 6.5J x 16; 7.5J x 17 |
INTRODUCTION
The GMC Sierra 2500HD III, in its 6.0L V8 automatic guise, represented a significant offering in the heavy-duty truck segment. Produced between 2007 and 2010, it was part of the GMT900 platform, shared with the Chevrolet Silverado 2500HD and Cadillac Escalade HD. This generation marked a substantial upgrade in terms of interior refinement, towing capacity, and overall build quality compared to its predecessors. The Extended Cab Long Box configuration provided a useful blend of passenger space and cargo bed length, making it suitable for both work and family needs. This particular variant, with its 360 horsepower engine and automatic transmission, aimed to provide a more accessible entry point into the heavy-duty truck market compared to the more expensive and powerful diesel options.
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD lay the Vortec LY6 6.0-liter V8 engine. This engine, a member of GM’s Vortec family, was known for its robust construction and relatively simple design. It featured a cast iron block and aluminum cylinder heads, contributing to its durability. The LY6 utilized a multi-port fuel injection system, delivering fuel directly to each cylinder for efficient combustion. The overhead valve (OHV) valvetrain, while not as technologically advanced as overhead cam designs, was reliable and cost-effective. The engine produced 360 horsepower at 5400 rpm and 515 Nm (379.84 lb-ft) of torque at 4200 rpm. Paired with the engine was the Hydra-Matic 6-speed automatic transmission. This transmission offered smooth shifting and helped to optimize the engine’s power delivery for both towing and everyday driving. The transmission was chosen for its durability and ability to handle the high torque output of the 6.0L V8.
Driving Characteristics
The 6.0L V8 and 6-speed automatic combination in the Sierra 2500HD delivered a driving experience focused on usability and capability. While not as quick as some of the lighter-duty trucks or those equipped with the diesel engine, it provided ample power for towing and hauling substantial loads. The automatic transmission’s gear ratios were tuned to prioritize low-end torque, making it easy to get heavy trailers moving. Compared to the manual transmission versions, the automatic offered greater convenience, especially in stop-and-go traffic. However, the manual transmission generally provided slightly better fuel economy and a more direct connection to the engine. Compared to the 6.6L Duramax diesel, the 6.0L V8 was noticeably less powerful and had a lower towing capacity, but it was also significantly less expensive to purchase and maintain.
Equipment & Trim Levels
The Sierra 2500HD III in this configuration typically came standard with features like air conditioning, power windows and locks, and a basic audio system. The Extended Cab provided seating for five passengers, with a small rear bench seat. Trim levels varied, but common options included upgraded cloth or leather upholstery, a premium audio system, power-adjustable seats, and a navigation system. Exterior options included chrome bumpers, running boards, and various wheel and tire packages. The SLE and SLT trims were the most common, offering a step up in features and interior appointments compared to the base WT (Work Truck) model.
Chassis & Braking
The Sierra 2500HD’s chassis was designed for heavy-duty use. It featured a fully boxed frame for increased rigidity and strength. The front suspension utilized an independent torsion bar and double wishbone setup, providing a comfortable ride while maintaining good handling characteristics. The rear suspension employed a traditional leaf spring design, optimized for load-carrying capacity. Braking duties were handled by ventilated disc brakes on all four wheels, with ABS (Anti-lock Braking System) as standard equipment. The rear brakes were slightly smaller in diameter than the front brakes. The truck’s robust suspension and braking system were essential for safely managing the high weight and towing capabilities of the vehicle.
Market Reception & Comparison
The GMC Sierra 2500HD with the 6.0L V8 and automatic transmission was generally well-received by critics and consumers. It was praised for its strong towing capacity, comfortable ride, and relatively affordable price point. However, some reviewers noted that the fuel economy was not particularly impressive, especially when towing heavy loads. Compared to the diesel-powered Sierra 2500HD, the 6.0L V8 offered a lower initial cost but sacrificed some performance and fuel efficiency. Against competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD held its own, offering a competitive combination of features, capability, and value.
Legacy
The 6.0L Vortec V8 engine, when paired with the Hydra-Matic transmission, proved to be a relatively reliable powertrain. While not immune to issues like oil consumption and occasional Active Fuel Management (AFM) problems, it generally held up well over time with proper maintenance. Today, these trucks can be found on the used car market at relatively affordable prices, making them a popular choice for those needing a capable work truck. However, potential buyers should be aware of the potential for oil consumption issues and should thoroughly inspect the vehicle before purchasing. The GMT900 generation Sierra 2500HD, and particularly this 6.0L V8 automatic variant, remains a testament to GM’s commitment to building durable and capable heavy-duty trucks.
