The GMC Sierra 3500HD IV (GMTK2XX) Crew Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower and paired with an Allison automatic transmission, 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 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) Crew 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 | 7.5 kg/Hp, 132.9 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 368.6 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 | 3348 kg (7381.08 lbs.) |
| Max. weight | 5171 kg (11400.1 lbs.) |
| Max load | 1823 kg (4019.03 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 | 1979 mm (77.91 in.) |
| Wheelbase | 4259 mm (167.68 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Minimum turning circle (turning diameter) | 17.1 m (56.1 ft.) |
| Drivetrain Architecture | Rear wheel drive |
| Number of gears and type of gearbox | 6 gears, automatic transmission Allison |
| Front suspension | Coil spring, Double wishbone, Wishbone |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 355×40 mm |
| Rear brakes | Ventilated discs, 373×34 mm |
| 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 Crew Cab Long Box with the 6.6L Duramax diesel and Allison automatic was positioned as a workhorse for serious hauling and towing. It built upon the foundation of the GMTK2XX platform, which emphasized increased strength and capability. The Crew Cab configuration offered ample passenger space, making it suitable for both work and family use, while the Long Box provided a generous cargo bed. This particular configuration was a popular choice for those needing the power of the Duramax engine without the complexity or cost of four-wheel drive.
Powertrain & Engine Architecture
At the heart of this Sierra 3500HD lies 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 torque. The engine’s overhead valve (OHV) valvetrain, while seemingly traditional, is known for its durability and reliability.
The Allison 1000 Series six-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. This transmission is renowned for its durability and smooth shifting characteristics. It features a torque converter lock-up clutch that engages in multiple gears, improving fuel efficiency. The transmission’s control system is integrated with the engine management system, optimizing shift points for both performance and economy.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by this powertrain combination translate into impressive real-world performance. While not as quick off the line as gasoline-powered trucks, the Duramax provides a broad, flat torque curve, making it exceptionally capable when towing or hauling heavy loads. The Allison transmission’s six gears allow the engine to operate within its optimal power band, even at highway speeds. Compared to the 6.0L gasoline V8 offered in the Sierra 3500HD, the Duramax provides significantly more torque, making it the preferred choice for demanding tasks. Compared to the 1.9L turbo diesel available in some other GMC models, this engine offers a substantial power increase, but at the cost of fuel economy.
Equipment & Trim Levels
The Sierra 3500HD Crew 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 rearview camera, and a basic infotainment system. Higher trim levels, such as the SLT and Denali, added 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 focused on functionality and durability, with comfortable seating and easy-to-use controls.
Chassis & Braking
The Sierra 3500HD’s chassis is built for strength and rigidity. It features a fully boxed frame constructed from high-strength steel. The front suspension utilizes coil springs and a double wishbone design, providing a comfortable ride and precise handling. The rear suspension employs a traditional leaf spring setup, optimized for load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when heavily loaded. An Anti-lock Braking System (ABS) is standard, enhancing safety and control. 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 engine received generally positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, and comfortable ride. Fuel economy, while respectable for a heavy-duty truck, was a common point of discussion, with some reviewers noting that it lagged behind competitors in certain tests. Compared to 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’s reputation for reliability also contributed to its strong market position.
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, and are sought after by those needing a capable and dependable work truck. While modern diesel engines are becoming increasingly complex, the L5P remains relatively straightforward to maintain, making it a popular choice for owners who prefer to perform their own repairs. The GMTK2XX platform also proved to be robust, with many examples still in service today, logging hundreds of thousands of miles. This Sierra 3500HD represents a high point in GMC’s heavy-duty truck history, offering a compelling combination of power, capability, and comfort.
