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, targeting buyers requiring substantial towing and hauling capabilities combined with a degree of comfort and refinement. It was part of the fourth generation (GMTK2XX) of the Sierra/Silverado HD platform, known for its increased strength and improved features over 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) 4WD 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 | 8 kg/Hp, 124.5 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 345.4 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 capacity | 29.7 l (31.38 US qt | 26.13 UK qt) |
| Kerb Weight | 3573 kg (7877.12 lbs.) |
| Max. weight | 5908 kg (13024.91 lbs.) |
| Max load | 2335 kg (5147.79 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 | 16.1 m (52.82 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, 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. Built on the GMTK2XX platform, this generation of Sierra HD trucks represented a move towards increased capability and refinement. The Double Cab configuration offered a balance between passenger space and bed length, making it suitable for both work and family needs. The Duramax engine, paired exclusively with the Allison transmission in this configuration, was the top-tier powertrain option, commanding a premium price and appealing to customers who prioritized performance and longevity.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a significant evolution of the Duramax design, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly. The L5P utilizes a Bosch common rail fuel injection system capable of extremely high injection pressures, contributing to its power and efficiency. The turbocharger, coupled with an intercooler, provides increased air density for improved combustion. The engine employs an overhead valve (OHV) valvetrain, a design choice favored for its durability and low-end torque characteristics.
The Allison 1000 series six-speed automatic transmission is specifically engineered to handle the immense torque output of the Duramax engine. This transmission is renowned for its durability and smooth shifting, utilizing a torque converter lock-up clutch to improve fuel efficiency at cruising speeds. The transmission is electronically controlled, optimizing shift points based on driving conditions and throttle input.
Driving Characteristics
The combination of the 445 horsepower and 910 lb-ft of torque delivered by the Duramax/Allison powertrain results in impressive performance, even when heavily loaded. While not a sports truck, the Sierra 3500HD offers ample power for merging onto highways and maintaining speed on inclines while towing. The Allison transmission’s well-chosen gear ratios contribute to a smooth and controlled driving experience. Compared to the gasoline-powered Sierra 3500HD models, the diesel offers significantly more low-end torque, making it far more capable for demanding tasks. Compared to other Duramax configurations, the 445 hp version provides a noticeable power increase over earlier iterations, enhancing its overall performance.
Equipment & Trim Levels
The Sierra 3500HD Double Cab Long Box with the Duramax engine typically came standard with a well-equipped interior. Features included cloth or leather upholstery (depending on the trim level – SLE, SLT, or Denali), air conditioning, power windows and locks, and a basic infotainment system. Higher trim levels, such as the SLT and Denali, added features like heated and ventilated seats, a premium audio system, navigation, and advanced safety technologies. Optional extras included a sunroof, upgraded wheels, and various appearance packages.
Chassis & Braking
The Sierra 3500HD’s chassis is built for heavy-duty use, featuring a fully boxed frame and robust suspension components. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs leaf springs. This configuration 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 equipment. The Dual Rear Wheel (DRW) configuration further enhances stability and load capacity.
Market Reception & Comparison
The GMC Sierra 3500HD with the Duramax/Allison combination received generally positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, and impressive towing capabilities. Fuel economy, while not exceptional, was considered reasonable for a heavy-duty truck of its size and capability. Compared to the gasoline-powered Sierra 3500HD models, the diesel offered superior fuel efficiency when towing and a significantly higher resale value. Reliability was generally good, although diesel engines can be more expensive to maintain than gasoline engines due to the complexity of the fuel injection system and emissions controls.
Legacy
The Duramax L5P engine and Allison transmission pairing has proven to be exceptionally durable and reliable. These trucks continue to hold their value well in the used car market, particularly those that have been well-maintained. The 2017-2019 Sierra 3500HD represents a sweet spot in the GMTK2XX generation, offering a blend of proven technology, robust construction, and a comfortable interior. The powertrain is known for its longevity, and with proper maintenance, these trucks can provide many years of reliable service. They remain a popular choice for owners who require a capable and dependable heavy-duty truck.
