Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD IV (GMTK2XX) Crew 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 | 8.2 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 | 6563 mm, 258.39 in |
| Width including mirrors | 2045 mm, 80.51 in |
| Height | 1981 mm, 77.99 in |
| Wheelbase | 4258 mm, 167.64 in |
| Front track | 1748 mm, 68.82 in |
| Rear (Back) track | 1709 mm, 67.28 in |
| Ride height (ground clearance) | 211 mm, 8.31 in |
| Minimum turning circle (turning diameter) | 17.1 m, 56.1 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 | Coil spring, Double wishbone, Transverse stabilizer |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 350×40 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 |
The 2015-2017 GMC Sierra 2500HD Crew Cab Long Box, equipped with the 6.6-liter Duramax turbo-diesel V8 engine and Allison automatic transmission, was a significant model in GMC’s heavy-duty truck lineup. Built on the GMTK2XX platform, this generation marked a substantial improvement in capability, refinement, and available technology. The Crew Cab configuration offered generous passenger space, while the Long Box provided a substantial cargo bed. This specific variant was positioned as a premium offering, targeting buyers who needed a powerful and capable truck for work or recreational towing, but also desired a comfortable and well-equipped interior.
Powertrain & Engine Architecture
The heart of this Sierra 2500HD is the Duramax LML 6.6-liter turbocharged diesel V8 engine. This engine is well-regarded for its durability and substantial torque output. The LML iteration featured a revised turbocharger, an improved fuel injection system, and an enhanced glow plug system compared to earlier Duramax designs. The engine utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion efficiency. The valvetrain employs an overhead valve (OHV) configuration, favored for its simplicity and proven reliability. Paired with the engine is the Allison 1000 six-speed automatic transmission, specifically engineered to manage the immense torque produced by the Duramax. This transmission incorporates a lock-up torque converter to enhance fuel economy and a heavy-duty cooling system to prevent overheating during demanding use. The transmission’s gear ratios are carefully calibrated for both towing and everyday driving, providing a balance between power delivery and efficiency.
Driving Characteristics
The combination of 397 horsepower and 765 lb-ft of torque from the Duramax/Allison powertrain delivers impressive real-world performance. While not offering the rapid acceleration of gasoline-powered trucks, the Sierra 2500HD truly shines when towing and hauling. The Allison transmission provides smooth and precise shifts, and the engine’s abundant low-end torque makes pulling heavy loads effortless without requiring frequent downshifting. Compared to the available 6.0L gasoline V8 option, the Duramax offered significantly more torque and improved fuel economy, particularly when towing substantial weight. The automatic transmission, while convenient, did result in a slight performance difference compared to the available manual transmission, particularly in terms of immediate responsiveness. However, the Allison’s programming minimized this difference, providing a generally satisfying driving experience.
Equipment & Trim Levels
The Sierra 2500HD Crew Cab Long Box with the Duramax engine was typically offered in higher trim levels, such as SLE and Denali. Standard features generally included air conditioning, power windows and locks, a rearview camera, and a basic infotainment system. Higher trim levels 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 wheel options, and various towing packages tailored to specific needs. The interior design prioritized functionality and durability, offering comfortable seating and intuitive controls.
Chassis & Braking
The GMTK2XX platform provided a robust foundation for the Sierra 2500HD. The chassis featured a fully boxed frame for increased rigidity and strength. The front suspension utilized coil springs and a double wishbone design, while the rear suspension employed leaf springs. This configuration provided a comfortable ride while maintaining excellent load-carrying capacity. Braking was handled by ventilated disc brakes on all four wheels, providing ample stopping power even when towing heavy loads. An Anti-lock Braking System (ABS) was standard equipment. Rear axle ratios varied depending on the specific configuration, influencing both towing capacity and fuel economy.
Market Reception & Comparison
The GMC Sierra 2500HD with the Duramax diesel engine consistently received positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, comfortable ride, and spacious interior. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD offered a compelling blend of capability and refinement. While the initial cost was higher than gasoline-powered models, the Duramax engine’s superior fuel economy and long-term durability often made it a worthwhile investment for heavy-duty users. Reliability was generally good, although some owners reported occasional issues with the diesel particulate filter (DPF) system, a common concern with modern diesel engines.
Legacy
The Duramax LML engine and Allison transmission pairing in the 2015-2017 GMC Sierra 2500HD has proven to be a durable and reliable powertrain. These trucks continue to hold their value in the used car market, particularly those that have been well-maintained. The LML Duramax is known for its longevity and relatively low maintenance costs, making it a popular choice for buyers seeking a capable and dependable heavy-duty truck. While newer generations of the Sierra 2500HD offer even more advanced technology and features, the GMTK2XX platform remains a respected and capable platform for those needing a robust work truck.
