The GMC Sierra 2500HD III, specifically the Extended Cab Standard Box configuration with the 6.0-liter V8 engine and automatic transmission, was produced from 2007 to 2010 as part of the GMT900 series. This heavy-duty pickup truck represented GMC’s offering in the increasingly popular 2500-class segment, designed for buyers needing substantial towing and payload capacity. Positioned as a workhorse, this variant sat in the middle of the Sierra 2500HD lineup, offering a balance between capability and affordability compared to the diesel-powered options and higher trim levels. It was a key competitor to the Ford Super Duty and Dodge Ram 2500 series trucks.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900) Extended Cab Standard 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 kg/Hp, 142.3 Hp/tonne |
| Weight-to-torque ratio | 4.9 kg/Nm, 203.6 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 | 2529 kg, 5575.49 lbs. |
| Max. weight | 4173 kg, 9199.89 lbs. |
| Max load | 1644 kg, 3624.4 lbs. |
| Trunk (boot) space – maximum | 1718 l, 60.67 cu. ft. |
| Fuel tank capacity | 98 l, 25.89 US gal | 21.56 UK gal |
| Permitted trailer load with brakes (12%) | 5761 kg, 12700.83 lbs. |
| Length | 5850 mm, 230.31 in. |
| Width including mirrors | 2032 mm, 80 in. |
| Height | 1951 mm, 76.81 in. |
| Wheelbase | 3645 mm, 143.5 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) | 14.5 m, 47.57 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 |
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD variant lies the Vortec LY6 engine, a 6.0-liter (364 cubic inch) V8. 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 utilizes a multi-port fuel injection system for precise fuel delivery. 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 lb-ft of torque at 4200 rpm. The Hydra-Matic 6-speed automatic transmission was the standard gearbox, providing smooth shifts and adequate gear ratios for both towing and everyday driving. This transmission was chosen for its durability and ability to handle the engine’s substantial torque output.
Driving Characteristics
The 6.0L V8 and 6-speed automatic combination in the Sierra 2500HD delivered a capable, if not particularly sporty, driving experience. Acceleration was adequate for a heavy-duty truck, but the focus was clearly on low-end torque for towing and hauling. The automatic transmission’s gear ratios were optimized for pulling loads, with a relatively quick downshift response when needed. Compared to the available Duramax diesel engine, the 6.0L V8 offered less torque and lower fuel economy, but it was quieter and less expensive to maintain. Compared to the manual transmission options, the automatic provided greater convenience, especially in stop-and-go traffic, but sacrificed some driver control and potentially some fuel efficiency.
Equipment & Trim Levels
The Extended Cab Standard Box 6.0L Automatic Sierra 2500HD typically came standard with features like air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. The Extended Cab configuration provided additional rear seating, though legroom was limited. Optional extras included upgraded audio systems, power-adjustable seats, a towing package (including trailer brake controller), and various appearance packages. Higher trim levels, such as the LT and SLT, added features like leather upholstery, chrome exterior trim, and more advanced audio systems. The standard box length offered a good balance between cargo space and maneuverability.
Chassis & Braking
The Sierra 2500HD’s chassis was built for heavy-duty use. It featured a fully boxed frame for increased rigidity and strength. The front suspension utilized an independent torsion bar setup with double wishbones, providing a relatively comfortable ride for a truck of this size. 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 discs were slightly smaller in diameter than the front, reflecting the lower weight distribution at the rear of the vehicle.
Market Reception & Comparison
The 6.0L V8-powered Sierra 2500HD received generally positive reviews for its capability and value. Critics praised its strong towing capacity and comfortable ride, but noted that its fuel economy was significantly lower than that of the diesel-powered alternatives. Compared to the Duramax diesel, the 6.0L V8 was seen as a more affordable option for buyers who didn’t require the ultimate in towing performance. The gasoline engine also benefited from lower maintenance costs, as diesel engines typically require more frequent and expensive servicing. However, the diesel engine held its resale value better due to its superior fuel economy and towing capabilities.
Legacy
The GMT900-generation Sierra 2500HD, including the 6.0L V8 Automatic variant, remains a popular choice in the used truck market. The Vortec LY6 engine is known for its reliability, although it is susceptible to oil consumption issues if not properly maintained. The Hydra-Matic transmission is also generally durable, but regular fluid changes are essential for long-term reliability. These trucks are often sought after by those needing a capable work truck without the higher price tag and maintenance costs associated with diesel engines. Today, well-maintained examples can still provide years of reliable service, making them a practical and affordable option for those requiring heavy-duty capability.
