The Chevrolet Silverado 2500 HD II, specifically the Extended Cab Long Box configuration powered by the 6.6-liter Duramax turbodiesel V8 and paired with an Allison automatic transmission, represents a significant iteration in Chevrolet’s heavy-duty truck lineage. Produced from 2007 to 2010 (GMT900 platform), this variant was aimed at buyers needing substantial towing and hauling capacity without sacrificing everyday usability. It occupied a sweet spot in the 2500HD lineup, offering a balance between the base work truck trims and the more luxurious LTZ models. This particular combination of engine and transmission became a popular choice for those requiring serious capability, particularly in applications like construction, farming, and recreational towing.
Technical Specifications
| Brand | Chevrolet |
| Model | Silverado 2500 HD |
| Generation | Silverado 2500 HD II (GMT900) Extended Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (365 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 | Diesel |
| Weight-to-power ratio | 8 kg/Hp, 125.2 Hp/tonne |
| Weight-to-torque ratio | 3.3 kg/Nm, 307 Nm/tonne |
| Power | 365 Hp @ 3200 rpm |
| Power per litre | 55.3 Hp/l |
| Torque | 895 Nm @ 1600 rpm (660.12 lb.-ft. @ 1600 rpm) |
| Maximum engine speed | 3450 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax LMM |
| Engine displacement | 6599 cm3 (402.7 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 103 mm (4.06 in.) |
| Piston Stroke | 99 mm (3.9 in.) |
| Compression ratio | 16.8:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | OHV |
| Engine oil capacity | 9.5 l (10.04 US qt | 8.36 UK qt) |
| Coolant | 24 l (25.36 US qt | 21.12 UK qt) |
| Kerb Weight | 2915 kg (6426.47 lbs.) |
| Max. weight | 4173 kg (9199.89 lbs.) |
| Max load | 1258 kg (2773.42 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%) | 5897 kg (13000.66 lbs.) |
| Length | 6330 mm (249.21 in.) |
| Width including mirrors | 2032 mm (80 in.) |
| Height | 1946 mm (76.61 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 | Rear wheel drive |
| Number of gears and type of gearbox | 6 gears, automatic transmission Allison |
| 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 |
| Tires size | 245/75 R16; 265/75 R17 |
| Wheel rims size | 6.5J x 16; 7.5J x 17 |
Powertrain & Engine Architecture
The heart of this Silverado 2500 HD II is the Duramax LMM 6.6-liter V8 diesel engine. This engine represented a significant evolution of the Duramax platform, building upon the success of the LBZ engine. The LMM featured a redesigned combustion chamber and improved fuel injection system, contributing to increased power and reduced emissions. The engine utilizes a common-rail direct injection system, delivering fuel at extremely high pressures for optimal combustion. The turbocharger, coupled with an intercooler, provides increased air intake, further enhancing performance. The engine’s valvetrain employs an overhead valve (OHV) configuration, known for its simplicity and durability. The Allison 1000 six-speed automatic transmission is a crucial component, specifically engineered to handle the immense torque output of the Duramax engine. This transmission is renowned for its robustness and smooth shifting characteristics, making it ideal for heavy-duty applications.
Driving Characteristics
The 365 horsepower and 895 lb-ft of torque delivered by the Duramax/Allison combination provided substantial performance for a heavy-duty truck. While not as quick as gasoline-powered counterparts, the Silverado 2500 HD II excelled in towing and hauling. The Allison transmission’s gear ratios were optimized for maximizing torque at lower RPMs, providing strong acceleration even when heavily loaded. Compared to the 1.8L gasoline engine options available in the Silverado 1500, this diesel offered a vastly different driving experience – prioritizing pulling power over outright speed. The automatic transmission, while convenient, did result in a slight reduction in fuel economy compared to the available manual transmission, but the trade-off in ease of use was often considered worthwhile by many drivers.
Equipment & Trim Levels
The Extended Cab Long Box 6.6 Duramax configuration typically fell into the mid-range of Silverado 2500 HD trim levels. Standard features included air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. The Extended Cab provided additional rear seating, though legroom was limited. Optional extras included leather upholstery, a premium audio system, navigation, and various towing packages. The Long Box configuration offered a generous bed length, ideal for hauling large items. The interior, while functional, was generally more utilitarian than the higher-end LTZ trims, focusing on durability and practicality.
Chassis & Braking
The Silverado 2500 HD II featured a robust chassis designed to withstand heavy loads. The front suspension utilized an independent torsion bar setup with double wishbones, providing a comfortable ride while maintaining stability. The rear suspension employed a traditional leaf spring configuration, known for its load-carrying capacity. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) was standard. The rear axle ratios were typically geared towards maximizing towing capacity, which could slightly impact fuel economy at highway speeds.
Market Reception & Comparison
The 6.6 Duramax/Allison combination was widely praised by automotive critics and truck enthusiasts alike. It was consistently lauded for its impressive towing capacity, smooth shifting transmission, and relatively quiet operation for a diesel engine. Compared to the gasoline engine options, the Duramax offered significantly better fuel economy when towing heavy loads. However, the diesel engine carried a higher initial cost and potentially higher maintenance expenses. Compared to the lighter-duty Silverado 1500 models, the 2500 HD provided a much more capable platform for serious work, but at the expense of ride comfort and maneuverability.
Legacy
The Duramax LMM engine and Allison transmission pairing proved to be exceptionally durable and reliable. Well-maintained examples of the 2007-2010 Silverado 2500 HD II continue to command strong resale values in the used car market. The engine is known for its longevity, with many units exceeding 200,000 miles with proper maintenance. The Allison transmission is also highly regarded for its reliability. These trucks remain a popular choice for those seeking a capable and dependable heavy-duty workhorse, and are often sought after by those needing a robust platform for towing and hauling. The GMT900 platform, and specifically this Duramax configuration, solidified Chevrolet’s reputation for building tough and capable trucks.
