The GMC Sierra 3500HD IV (GMTK2XX) Crew Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine and an Allison automatic transmission, represents a significant iteration in GMC’s heavy-duty truck lineage. Produced from 2015 to 2017, this variant occupied a premium position within the Sierra 3500HD lineup, catering to buyers requiring substantial towing and hauling capabilities combined with a comfortable, well-equipped cabin. It was part of the fourth generation of the Sierra/Silverado HD trucks, known as the GMTK2XX platform, which brought substantial improvements in capability, refinement, and technology.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD IV (GMTK2XX) Crew Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (397 Hp) DRW Automatic |
| Start of production | 2015 |
| End of production | 2017 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.7 kg/Hp, 114.4 Hp/tonne |
| Weight-to-torque ratio | 3.3 kg/Nm, 298.9 Nm/tonne |
| Power | 397 Hp @ 3000 rpm |
| Power per litre | 60.2 Hp/l |
| Torque | 1037 Nm @ 1600 rpm (764.85 lb.-ft. @ 1600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax LML |
| Engine displacement | 6599 cm3 (402.7 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 | 3469 kg (7647.84 lbs.) |
| Max. weight | 5908 kg (13024.91 lbs.) |
| Max load | 2439 kg (5377.07 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 | 6563 mm (258.39 in.) |
| Width including mirrors | 2438 mm (95.98 in.) |
| Height | 1976 mm (77.8 in.) |
| Wheelbase | 4259 mm (167.68 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1906 mm (75.04 in.) |
| Ride height (ground clearance) | 210 mm (8.27 in.) |
| Minimum turning circle (turning diameter) | 17 m (55.77 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, 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 2015-2017 GMC Sierra 3500HD Crew Cab Long Box with the 6.6L Duramax diesel and Allison automatic was positioned as a premium work truck, designed for owners who frequently tow large trailers or haul heavy loads. The “HD” designation signifies Heavy Duty, indicating a robust chassis and powertrain engineered for demanding tasks. The Crew Cab configuration offered spacious seating for five passengers, while the Long Box provided ample cargo space. This particular model year represented a mid-cycle refresh of the GMTK2XX platform, incorporating updated styling and enhanced features.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax LML 6.6-liter turbocharged diesel V8. This engine is renowned for its durability and impressive torque output. The LML engine builds upon the previous LLY, LBZ, and LMM Duramax designs, incorporating a redesigned turbocharger, improved fuel injection system, and enhanced cooling. The engine utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressure for optimized combustion. The valvetrain employs an overhead valve (OHV) configuration, known for its simplicity and reliability. The Allison 1000 six-speed automatic transmission is specifically designed to handle the immense torque produced by the Duramax engine. This transmission features a lock-up torque converter for improved fuel efficiency and a heavy-duty cooling system to prevent overheating during demanding use. The transmission’s gear ratios are optimized for both towing and everyday driving, providing a balance of power and efficiency.
Driving Characteristics
The 397 horsepower and 764.85 lb-ft of torque delivered by the Duramax/Allison combination provide exceptional towing and hauling capabilities. While not a performance-oriented truck, the Sierra 3500HD offers ample power for accelerating with a load or maintaining highway speeds. The Allison transmission shifts smoothly and decisively, providing a comfortable driving experience. Compared to the gasoline-powered Sierra 3500HD models, the diesel variant offers significantly more torque at lower RPMs, making it ideal for towing. 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. The dual rear wheels (DRW) configuration further enhances stability and load-carrying capacity.
Equipment & Trim Levels
The Sierra 3500HD was available in various trim levels, with the Denali being the most luxurious. Even in lower trims, the Crew Cab Long Box models typically included features such as air conditioning, power windows and locks, a tilt steering wheel, and a basic audio system. Higher trims added features like leather upholstery, heated and ventilated front seats, a premium audio system, navigation, and advanced safety technologies. Optional extras included a sunroof, a rear-seat entertainment 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 features a fully boxed frame constructed from high-strength steel, providing a solid foundation for the truck’s heavy-duty capabilities. 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 a heavy load. An Anti-lock Braking System (ABS) is standard, enhancing safety and control. The DRW configuration provides a wider stance and increased braking capacity.
Market Reception & Comparison
The GMC Sierra 3500HD with the Duramax diesel and Allison automatic was generally well-received by critics and consumers alike. It was praised for its powerful engine, smooth transmission, and comfortable ride. Compared to the gasoline-powered Sierra 3500HD models, the diesel variant offered superior towing and hauling capabilities, albeit at a higher price point. Compared to competitors like the Ford Super Duty and Ram Heavy Duty trucks, the Sierra 3500HD was often considered to be a more refined and comfortable option. Fuel economy, while not a primary concern for heavy-duty truck buyers, was respectable for a vehicle of this size and capability. Reliability was generally good, although diesel engines can be more expensive to maintain than gasoline engines.
Legacy
The Duramax LML engine and Allison 1000 transmission have proven to be exceptionally durable and reliable powertrains. Well-maintained examples of the 2015-2017 GMC Sierra 3500HD continue to command strong resale values in the used car market. These trucks remain popular among owners who require a capable and dependable work truck. The GMTK2XX platform established a new benchmark for heavy-duty truck refinement and capability, and the Duramax/Allison combination remains a highly sought-after powertrain option for those who demand the best in towing and hauling performance.
