The GMC Sierra 2500HD IV (GMTK2XX) Double Cab Standard Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 397 horsepower and paired with a 6-speed Allison automatic transmission and four-wheel drive, was a prominent offering in the heavy-duty pickup truck segment from 2015 to 2017. This configuration represented a sweet spot in the Sierra 2500HD lineup, balancing substantial towing and hauling capability with a degree of everyday usability. It was positioned as a workhorse for those needing more than a light-duty truck could offer, but didn’t necessarily require the absolute maximum capabilities of the top-trim models.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD IV (GMTK2XX) Double Cab Standard 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 | 8.3 kg/Hp, 120.9 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 315.8 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 | 3284 kg (7239.98 lbs.) |
| Max. weight | 4536 kg (10000.17 lbs.) |
| Max load | 1252 kg (2760.19 lbs.) |
| Trunk (boot) space – maximum | 1728 l (61.02 cu. ft.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 5897 kg (13000.66 lbs.) |
| Length | 5842 mm (230 in.) |
| Width including mirrors | 2045 mm (80.51 in.) |
| Height | 1983 mm (78.07 in.) |
| Wheelbase | 3662 mm (144.17 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) | 15 m (49.21 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 | Coil spring, Double wishbone, Transverse stabilizer |
| 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 GMC Sierra 2500HD Double Cab Standard Box with the 6.6L Duramax diesel and Allison automatic transmission represented the fourth generation (GMTK2XX) of GMC’s heavy-duty pickup line. This generation, introduced in 2015, brought significant updates to the Sierra’s styling, interior, and technology. The Double Cab configuration offered a balance between passenger space and bed length, making it suitable for both work and family use. The 6.6L Duramax engine, a staple of GMC’s heavy-duty trucks, provided ample power and torque for demanding tasks, while the Allison transmission ensured smooth and reliable shifting. This particular variant aimed to provide a capable and comfortable truck for owners who frequently tow or haul, but didn’t necessarily need the maximum payload or towing capacity offered by higher trim levels.
Powertrain & Engine Architecture
The heart of this Sierra 2500HD 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. The LML Duramax utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The engine also incorporates a variable geometry turbocharger (VGT) and an intercooler to maximize power and efficiency. The valvetrain employs an overhead valve (OHV) configuration, known for its durability and simplicity.
The Allison 1000 6-speed automatic transmission is specifically designed to handle the high torque output of the Duramax engine. This transmission features a heavy-duty torque converter and robust internal components. The Allison transmission is renowned for its durability and smooth shifting characteristics, contributing significantly to the truck’s overall driving experience. Gear ratios are optimized for both towing and fuel economy, providing a balance between performance and efficiency.
Driving Characteristics
The 397 horsepower and 765 lb-ft of torque delivered by the Duramax engine and Allison transmission combination provide substantial pulling power. While not as quick off the line as gasoline-powered counterparts, the Sierra 2500HD excels in situations requiring low-end torque, such as towing heavy loads or navigating steep inclines. The Allison transmission shifts smoothly and predictably, minimizing gear hunting and providing a comfortable driving experience. Compared to the 6.0L gasoline V8 option, the Duramax offered significantly more torque, making it the preferred choice for those who regularly tow or haul. Compared to higher-output Duramax variants (available in some trims), this 397 hp version offered a slightly more relaxed driving experience, prioritizing fuel economy and refinement over outright performance.
Equipment & Trim Levels
The Double Cab Standard Box configuration typically came standard with features like air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. Higher trim levels, such as SLE and SLT, added features like leather upholstery, heated seats, a premium audio system, and advanced safety technologies. Optional extras included a navigation system, a rear-seat entertainment system, and various towing packages. The Standard Box bed length provided a practical cargo area for hauling materials, while the Double Cab offered comfortable seating for up to five passengers.
Chassis & Braking
The Sierra 2500HD features a fully boxed frame for enhanced rigidity and durability. The front suspension utilizes a coil spring and double wishbone design, while the rear suspension employs a leaf spring setup. This combination provides a comfortable ride while maintaining excellent load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when towing heavy loads. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations.
Market Reception & Comparison
The 2015-2017 GMC Sierra 2500HD with the 6.6L Duramax and Allison transmission was generally well-received by critics and consumers alike. It was praised for its powerful engine, smooth transmission, comfortable ride, and robust construction. Fuel economy, while not exceptional, was considered reasonable for a heavy-duty truck of its size and capability. Compared to the Ford Super Duty and Ram 2500, the Sierra 2500HD offered a competitive combination of features, performance, and reliability. The Duramax engine was often cited as a key advantage, offering superior torque and fuel efficiency compared to some of its competitors.
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 Sierra 2500HD continue to command strong resale values in the used car market. The combination of power, capability, and reliability makes this truck a popular choice for those seeking a heavy-duty pickup that can handle demanding tasks for years to come. Common maintenance items include regular oil changes, fuel filter replacements, and coolant flushes. Overall, this Sierra 2500HD variant represents a solid investment for those in need of a capable and dependable work truck.
