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 refinement. It was part of the fourth generation (GMTK2XX) of the Sierra/Silverado HD platform, known for its increased strength and improved interior 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) SRW 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 | 7.4 kg/Hp, 135.1 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 374.7 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 | 3293 kg (7259.82 lbs.) |
| Max. weight | 5080 kg (11199.48 lbs.) |
| Max load | 1787 kg (3939.66 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 | 1981 mm (77.99 in.) |
| Wheelbase | 4017 mm (158.15 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Minimum turning circle (turning diameter) | 16.2 m (53.15 ft.) |
| Drivetrain Architecture | 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, 373×34 mm |
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine represents a significant evolution of the Duramax design, incorporating a robust cast iron block, aluminum cylinder heads, and a high-pressure common rail fuel injection system. The L5P boasts a variable geometry turbocharger (VGT) and cooled exhaust gas recirculation (EGR) to optimize performance and reduce emissions. The engine’s OHV valvetrain contributes to its durability and low-end torque characteristics. Paired with the engine is the Allison 1000 six-speed automatic transmission, renowned for its durability and ability to handle high torque loads. This transmission features electronically controlled shifts and a lock-up torque converter for improved fuel efficiency.
Driving Characteristics
The combination of the 445 horsepower Duramax and the Allison automatic delivers a compelling driving experience. While not as overtly sporty as some lighter-duty trucks, the Sierra 3500HD provides ample power for towing and hauling heavy loads. The Allison transmission is well-tuned for this application, offering smooth and predictable shifts. The gear ratios are optimized for maximizing torque at lower RPMs, making it easy to pull trailers or carry substantial payloads. Compared to the 6.0L gasoline V8 option, the Duramax offers significantly more torque and better fuel economy, albeit at a higher initial cost. Compared to the 1.9L turbo diesel available in the smaller Sierra 1500, this engine is in a completely different league, focused on maximum capability rather than efficiency.
Equipment & Trim Levels
The Double Cab Long Box configuration offered a spacious interior with seating for five passengers. Standard features typically included air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, and a rearview camera. Higher trim levels, such as the Denali, added premium features like leather upholstery, heated and ventilated seats, a premium sound system, and advanced safety technologies. Optional extras included a sunroof, navigation system, and various towing packages. The interior design was functional and durable, reflecting the truck’s work-oriented purpose.
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 leaf springs. This setup is designed to handle heavy loads and provide a comfortable ride. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) is standard. The rear axle was typically a single rear wheel (SRW) configuration, though dual rear wheel (DRW) options were available for even greater towing capacity.
Market Reception & Comparison
The 2017-2019 GMC Sierra 3500HD with the Duramax diesel and Allison automatic received generally positive reviews. Critics praised its powerful engine, smooth transmission, and comfortable ride. Fuel economy, while not exceptional, was considered good for a heavy-duty truck of its size. Compared to competitors like the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as offering a good balance of capability, comfort, and refinement. The Duramax engine consistently ranked highly in reliability surveys, although diesel engines generally require more expensive maintenance than gasoline engines.
Legacy
The Duramax L5P engine has proven to be a remarkably durable and reliable powertrain. Well-maintained examples of the 2017-2019 Sierra 3500HD continue to command strong resale values in the used car market. The Allison transmission is also known for its longevity. However, potential buyers should be aware of the higher maintenance costs associated with diesel engines, including the potential for issues with the emissions control system (particulate filter). Overall, this variant of the Sierra 3500HD represents a capable and well-engineered heavy-duty truck that continues to be a popular choice for those needing serious towing and hauling capacity.
