The Chevrolet Silverado 2500HD III (K2XX) Double Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 397 horsepower and paired with an Allison automatic transmission, was a prominent offering in Chevrolet’s heavy-duty pickup truck lineup from 2015 to 2017. This configuration represented a sweet spot for buyers needing substantial towing and hauling capability without sacrificing everyday drivability. It sat firmly in the mid-to-upper range of the 2500HD trim levels, offering a balance between work-focused functionality and comfort features. The K2XX platform, introduced in 2014, brought significant improvements in ride quality, interior refinement, and overall capability compared to its predecessor.
Technical Specifications
| Brand | Chevrolet |
| Model | Silverado 2500 HD |
| Generation | Silverado 2500 HD III (K2XX) Double Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (397 Hp) Automatic |
| Start of production | 2015 year |
| End of production | 2017 year |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.1 kg/Hp, 124 Hp/tonne |
| Weight-to-torque ratio | 3.1 kg/Nm, 323.9 Nm/tonne |
| Power | 397 Hp @ 3000 rpm |
| Power per litre | 60.2 Hp/l |
| Torque | 1037 Nm @ 1600 rpm, 764.85 lb.-ft. @ 1600 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax LML |
| 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 | 16:1 |
| 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 | 22.4 l, 23.67 US qt | 19.71 UK qt |
| Kerb Weight | 3202 kg, 7059.2 lbs |
| Max. weight | 4536 kg, 10000.17 lbs |
| Max load | 1334 kg, 2940.97 lbs |
| Trunk (boot) space – maximum | 2162 l, 76.35 cu. ft |
| Fuel tank capacity | 136 l, 35.93 US gal | 29.92 UK gal |
| Permitted trailer load with brakes (12%) | 6577 kg, 14499.8 lbs |
| Length | 6321 mm, 248.86 in |
| Width including mirrors | 2045 mm, 80.51 in |
| Height | 1978 mm, 77.87 in |
| Wheelbase | 4017 mm, 158.15 in |
| Front track | 1748 mm, 68.82 in |
| Rear (Back) track | 1709 mm, 67.28 in |
| Ride height (ground clearance) | 216 mm, 8.5 in |
| Minimum turning circle (turning diameter) | 16.2 m, 53.15 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 Allison |
| Front suspension | Independent torsion bar, double wishbone |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 355×40 mm |
| Rear brakes | Ventilated discs, 360×34 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 245/75 R17; 265/70 R17; 265/70 R18; 265/60 R20 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 20 |
Powertrain & Engine Architecture
The heart of this Silverado 2500HD variant is the Duramax LML 6.6-liter turbocharged diesel V8. This engine is a testament to diesel engineering, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly designed for high torque output and longevity. The LML generation of the Duramax introduced a revised turbocharger, improved fuel injection system, and enhanced glow plug technology compared to previous iterations. The common-rail fuel injection system, capable of extremely high injection pressures, ensures efficient combustion and contributes to the engine’s impressive power and fuel economy. The overhead valve (OHV) valvetrain, while seemingly traditional, is known for its durability and simplicity. The Allison 1000 six-speed automatic transmission is a critical component, specifically engineered to handle the massive torque produced by the Duramax engine. This transmission features a lock-up torque converter for improved efficiency and a heavy-duty cooling system to prevent overheating under demanding conditions.
Driving Characteristics
The 397 horsepower and 764.85 lb-ft of torque delivered by this combination translate into formidable towing and hauling capabilities. While not as quick off the line as gasoline-powered counterparts, the Duramax provides a broad, flat torque curve, making it exceptionally capable at low speeds and when carrying heavy loads. The Allison transmission shifts smoothly and decisively, providing ample power for highway cruising and navigating challenging terrain. Compared to the 6.0-liter gasoline V8 option, the Duramax offered significantly more torque and better fuel economy, especially when towing. The automatic transmission, while convenient, did result in a slight performance deficit compared to the available six-speed manual transmission, which allowed for more driver control and potentially slightly better fuel efficiency. However, the automatic was favored by many drivers for its ease of use, particularly in stop-and-go traffic or when towing on long journeys.
Equipment & Trim Levels
The Double Cab Long Box configuration offered a spacious interior with seating for five passengers. Standard features typically included air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. Higher trim levels, such as the LT and LTZ, added features like leather upholstery, heated and ventilated front seats, a premium audio system, navigation, and advanced safety technologies. Optional extras included a sunroof, upgraded wheels, and various towing packages. The Double Cab configuration provided a useful rear seat area for passengers, while the Long Box offered ample cargo space for hauling equipment or supplies.
Chassis & Braking
The Silverado 2500HD utilized a fully boxed frame for enhanced rigidity and durability. The front suspension featured an independent torsion bar setup with double wishbone components, providing a comfortable ride and 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 at all four corners, with ABS standard. The rear brakes were slightly smaller in diameter than the front brakes, reflecting the weight distribution of the vehicle. The steering system utilized a recirculating ball mechanism, providing a robust and reliable steering feel.
Market Reception & Comparison
The 6.6-liter Duramax diesel engine was consistently praised for its power, reliability, and fuel efficiency. Critics noted the Silverado 2500HD’s comfortable ride quality, spacious interior, and impressive towing capacity. Compared to the gasoline-powered Silverado 2500HD, the Duramax diesel commanded a significant price premium, but many buyers considered the added cost worthwhile for the benefits it provided. The Duramax/Allison combination was often favorably compared to similar offerings from Ford and Ram, with the Silverado generally being recognized for its refined ride and user-friendly features. Fuel economy, while not exceptional, was significantly better than that of the gasoline engines, particularly when towing.
Legacy
The Duramax LML engine, paired with the Allison transmission, has proven to be a remarkably durable and reliable powertrain. Properly maintained examples of the 2015-2017 Silverado 2500HD continue to command strong resale values in the used car market. The engine is known for its ability to accumulate high mileage with minimal issues, provided regular maintenance is performed. While diesel engines can be more expensive to repair than gasoline engines, the longevity and capability of the Duramax LML make it a popular choice for buyers seeking a heavy-duty pickup truck that can withstand years of demanding use. The K2XX platform also contributed to the Silverado’s reputation for improved ride quality and overall refinement, solidifying its position as a leading contender in the heavy-duty truck segment.
