The GMC Sierra 3500HD IV (GMTK2XX) Crew 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 needing substantial towing and hauling capacity 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 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) 4WD 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 | 7.9 kg/Hp, 126.9 Hp/tonne |
| Weight-to-torque ratio | 2.8 kg/Nm, 351.9 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 | 3507 kg (7731.61 lbs.) |
| Max. weight | 5262 kg (11600.72 lbs.) |
| Max load | 1755 kg (3869.11 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%) | 6804 kg (15000.25 lbs.) |
| Length | 6563 mm (258.39 in.) |
| Width including mirrors | 2045 mm (80.51 in.) |
| Height | 1983 mm (78.07 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 | 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 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 |
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 features like a redesigned combustion chamber, improved fuel injection system, and a more robust block. The L5P utilizes a common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion efficiency and reduced emissions. The engine also features a variable geometry turbocharger (VGT) and an intercooler to maximize power and torque output. The overhead valve (OHV) valvetrain, while traditional, is known for its durability and reliability. The Allison 1000 six-speed automatic transmission is paired with the Duramax engine. This transmission is renowned for its strength and ability to handle the high torque output of the diesel engine, making it ideal for heavy-duty applications. The transmission features a lock-up torque converter for improved fuel efficiency at highway speeds.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by the Duramax engine and Allison transmission combination provide the Sierra 3500HD with exceptional towing and hauling capabilities. While not designed for outright speed, the truck offers ample power for accelerating with a load or maintaining highway speeds even on steep inclines. The Allison transmission’s gear ratios are optimized for both towing and fuel economy. Compared to the gasoline-powered versions of the Sierra 3500HD, this diesel variant offers significantly more torque at lower RPMs, making it easier to pull heavy trailers. Compared to other Duramax configurations, like those with slightly less power, this 445 hp version provides a noticeable increase in performance, particularly when fully loaded. The automatic transmission, while convenient, doesn’t offer the same level of control as a manual transmission, but it simplifies operation for drivers who primarily use the truck for work or towing.
Equipment & Trim Levels
The Crew 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 navigation system, a sunroof, and various towing packages. The interior design focused on functionality and durability, with materials chosen to withstand the demands of heavy-duty use.
Chassis & Braking
The Sierra 3500HD features a fully boxed frame designed for maximum strength and rigidity. The front suspension utilizes a coil spring and double wishbone setup with a transverse stabilizer bar, while the rear suspension employs a traditional leaf spring design. This configuration provides a comfortable ride while maintaining excellent load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels. The front brakes measure 355×40 mm, while the rear brakes are 360 mm. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations.
Market Reception & Comparison
The GMC Sierra 3500HD with the 6.6-liter Duramax engine and Allison transmission was generally well-received by critics and consumers alike. It was praised for its powerful engine, smooth-shifting transmission, and impressive towing capacity. 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 3500, the Sierra 3500HD offered a competitive combination of performance, features, and reliability. Some reviewers noted that the interior, while functional, lacked the refinement of some competitors.
Legacy
The Duramax L5P engine and Allison transmission pairing has proven to be exceptionally durable and reliable. These trucks continue to hold their value in the used car market, particularly those that have been well-maintained. The L5P engine is known for its longevity, with many examples exceeding 200,000 miles without major issues. However, like any diesel engine, proper maintenance, including regular oil changes and fuel filter replacements, is crucial for ensuring long-term reliability. The GMTK2XX platform Sierra 3500HD remains a popular choice for those needing a capable and dependable heavy-duty truck.
