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 a 6-speed Allison automatic transmission, represents a significant iteration in Chevrolet’s heavy-duty truck lineage. Produced from 2015 to 2017, this configuration occupied a premium position within the Silverado 2500HD lineup, targeting buyers requiring substantial towing and hauling capabilities without sacrificing everyday usability. It was part of the third generation of the K2XX platform, known for its increased strength and refinement compared to its predecessors.
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) 4WD Automatic |
| Start of production | 2015 |
| End of production | 2017 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.2 kg/Hp, 121.7 Hp/tonne |
| Weight-to-torque ratio | 3.1 kg/Nm, 317.9 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 | 3262 kg (7191.48 lbs.) |
| Max. weight | 4536 kg (10000.17 lbs.) |
| Max load | 1274 kg (2808.69 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 | 1977 mm (77.83 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) | 214 mm (8.43 in.) |
| Minimum turning circle (turning diameter) | 16.2 m (53.15 ft.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front wheels engaged via clutch. |
| 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 |
INTRODUCTION
The 2015-2017 Chevrolet Silverado 2500HD Double Cab Long Box with the 6.6L Duramax diesel and Allison automatic was designed to cater to the demands of the American truck buyer. This generation, built on the K2XX platform, represented a significant step forward in terms of capability, refinement, and interior space. The Double Cab configuration offered a more spacious rear seat compared to the standard cab, making it suitable for both work and family use, while the Long Box provided ample cargo capacity. The Duramax/Allison pairing was, and remains, a highly regarded combination for heavy-duty towing and hauling.
Powertrain & Engine Architecture
At the heart of this Silverado variant lies 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 crankshaft. The LML iteration of the Duramax introduced a revised turbocharger, improved fuel injection system, and enhanced glow plug technology for improved cold-start performance and reduced emissions. The engine utilizes a common-rail direct injection system, delivering fuel at extremely high pressures for optimal combustion. The overhead valve (OHV) valvetrain, while seemingly dated, is known for its durability and simplicity. The Allison 1000 six-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. It features a lock-up torque converter for improved fuel efficiency and a heavy-duty cooling system to prevent overheating under strenuous conditions. The transmission’s gear ratios are optimized for both towing and highway cruising.
Driving Characteristics
The Silverado 2500HD 6.6L Duramax/Allison combination delivers a driving experience characterized by immense pulling power and a surprisingly comfortable ride for a heavy-duty truck. While not a performance-oriented vehicle, the 397 horsepower and 765 lb-ft of torque provide effortless acceleration, even when heavily loaded. The Allison transmission shifts smoothly and decisively, providing ample power in each gear. Compared to the gasoline-powered Silverado 2500HD models, the Duramax diesel offers significantly more low-end torque, making it ideal for towing large trailers or hauling heavy payloads. The automatic transmission, while convenient, does result in a slight reduction in fuel economy compared to the available manual transmission, but the trade-off in ease of use is often considered worthwhile by many drivers. The gear ratios are tuned for maximizing torque at lower RPMs, which is crucial for towing.
Equipment & Trim Levels
The Silverado 2500HD Double Cab Long Box with the Duramax engine typically came well-equipped, often falling into the mid-to-upper trim levels (LT or LTZ). Standard features included air conditioning, power windows and locks, a rearview camera, and a basic infotainment system. Higher trim levels added features such as leather upholstery, heated and ventilated front seats, a premium sound system, navigation, and advanced safety technologies. Optional extras included a sunroof, upgraded wheels, and various towing packages. The interior design focused on functionality and durability, with comfortable seating and easy-to-use controls.
Chassis & Braking
The K2XX platform chassis provided a solid foundation for the Silverado 2500HD. The front suspension utilized an independent torsion bar setup with double wishbones, offering a comfortable ride and good handling. 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, providing ample stopping power even when towing. An Anti-lock Braking System (ABS) was standard. The heavy-duty chassis and suspension components were designed to withstand the stresses of frequent heavy hauling.
Market Reception & Comparison
The Silverado 2500HD with the Duramax/Allison combination received generally positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, comfortable ride, and impressive towing capacity. Compared to its rivals, such as the Ford Super Duty and Ram 2500, the Silverado 2500HD offered a competitive combination of features, performance, and value. Fuel economy, while respectable for a heavy-duty truck, was not a standout feature. Reliability was generally good, although some owners reported issues with the diesel particulate filter (DPF) system.
Legacy
The Duramax LML engine and Allison 1000 transmission have proven to be exceptionally durable and reliable powertrains. Well-maintained examples of the 2015-2017 Silverado 2500HD continue to command strong resale values in the used car market. The combination remains highly sought after by those needing a capable and dependable heavy-duty truck. The LML Duramax is known for its longevity, and with proper maintenance, can easily exceed 200,000 miles. The Allison transmission is equally robust, and is often considered one of the most reliable automatic transmissions available in a heavy-duty truck.
