The GMC Sierra 3500HD IV (GMTK2XX) Double Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower, represents a significant iteration in GMC’s heavy-duty truck lineage. Produced from 2017 to 2019, this variant occupied a premium position within the Sierra 3500HD lineup, catering to buyers requiring substantial towing and hauling capabilities combined with a degree of comfort and refinement. It was part of the fourth generation of the Sierra/Silverado HD trucks, known as the GMTK2XX platform, which brought substantial improvements in strength, technology, and interior space compared to its predecessors.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD IV (GMTK2XX) Double Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (445 Hp) DRW Automatic |
| Start of production | 2017 |
| End of production | 2019 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.7 kg/Hp, 129.1 Hp/tonne |
| Weight-to-torque ratio | 2.8 kg/Nm, 358.1 Nm/tonne |
| Power | 445 Hp @ 2800 rpm |
| Power per litre | 67.4 Hp/l |
| Torque | 1234 Nm @ 1600 rpm (910.15 lb.-ft. @ 1600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax L5P |
| Engine displacement | 6604 cm3 (403 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 | 29.7 l (31.38 US qt | 26.13 UK qt) |
| Kerb Weight | 3446 kg (7597.13 lbs.) |
| Max. weight | 5908 kg (13024.91 lbs.) |
| Max load | 2462 kg (5427.78 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%) | 9072 kg (20000.34 lbs.) |
| Length | 6321 mm (248.86 in.) |
| Width including mirrors | 2438 mm (95.98 in.) |
| Height | 1972 mm (77.64 in.) |
| Wheelbase | 4017 mm (158.15 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1906 mm (75.04 in.) |
| Minimum turning circle (turning diameter) | 16.1 m (52.82 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, 355×40 mm |
| Rear brakes | Ventilated discs, 355×40 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 235/80 R17; 265/70 R18 |
| Wheel rims size | 7.5J x 17; 8J x 18 |
INTRODUCTION
The 2017-2019 GMC Sierra 3500HD Double Cab Long Box with the 6.6L Duramax diesel and Allison automatic transmission was positioned as a workhorse for serious hauling and towing. It catered to customers like ranchers, contractors, and those needing to move heavy equipment regularly. The “Double Cab” configuration offered increased rear-seat space compared to the standard cab, while the “Long Box” provided a substantial cargo bed. This particular configuration, with the powerful Duramax engine and robust Allison transmission, represented a premium offering within the Sierra 3500HD range, commanding a higher price point than the gasoline-powered options.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a testament to modern diesel technology, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly. The L5P utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The turbocharger, coupled with an intercooler, provides increased air intake, boosting power and efficiency. The engine produces 445 horsepower at 2800 rpm and a massive 910 lb-ft of torque at 1600 rpm. The Allison 1000 Series six-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. This transmission is known for its durability and smooth shifting characteristics, crucial for heavy-duty applications. The transmission features a lock-up torque converter for improved fuel economy at highway speeds.
Driving Characteristics
The combination of the Duramax engine and Allison transmission delivers a driving experience focused on capability rather than outright speed. Acceleration is strong, particularly when leveraging the engine’s substantial low-end torque. The Allison transmission shifts smoothly and predictably, providing ample power for towing and hauling. Compared to the 6.0L gasoline V8 offered in the Sierra 3500HD, the Duramax provides significantly more torque, making it far superior for demanding tasks. While the gasoline engine might offer quicker acceleration when unladen, the Duramax excels when burdened with heavy loads. The gear ratios in the Allison transmission are optimized for towing, providing ample pulling power in lower gears and efficient cruising in higher gears. The ride quality, even unladen, is relatively comfortable for a heavy-duty truck, though it’s noticeably firmer than lighter-duty pickups.
Equipment & Trim Levels
The Sierra 3500HD Double Cab Long Box with the Duramax engine typically came well-equipped, even in its base trim. Standard features included air conditioning, power windows and locks, a basic infotainment system, and a rearview camera. Higher trim levels, such as the SLT and Denali, added features like leather upholstery, heated and ventilated front seats, a premium sound system, navigation, and advanced safety technologies. Optional extras included a gooseneck/fifth-wheel hitch, bed liner, and various appearance packages. The interior design focused on functionality and durability, with robust materials and a user-friendly layout.
Chassis & Braking
The Sierra 3500HD features a fully boxed frame constructed from high-strength steel, providing a solid foundation for heavy-duty use. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. This configuration is designed to maximize load-carrying capacity and stability. 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. The rear axle ratio varied depending on the specific configuration, influencing both towing capacity and fuel economy.
Market Reception & Comparison
The Duramax/Allison combination in the Sierra 3500HD was widely praised by automotive critics and truck enthusiasts alike. It consistently received high marks for its towing capacity, reliability, and overall performance. Compared to the Ford Super Duty and Ram 3500, the Sierra 3500HD with the Duramax was often considered a strong contender, particularly in terms of engine refinement and transmission smoothness. Fuel economy, while not a primary concern for heavy-duty truck buyers, was generally competitive with other diesel-powered trucks in its class. However, the higher initial cost of the Duramax engine and Allison transmission compared to gasoline options was a potential drawback for some buyers.
Legacy
The Duramax L5P engine and Allison 1000 transmission have proven to be exceptionally durable and reliable powertrains. Well-maintained examples of the 2017-2019 Sierra 3500HD continue to command strong resale values in the used car market. The engine is known for its longevity, with many examples exceeding 200,000 miles without major issues. The Allison transmission is equally robust, capable of withstanding years of heavy use. This combination remains a popular choice for buyers seeking a capable and dependable heavy-duty truck, solidifying its place as a significant chapter in GMC’s truck history.
