The GMC Sierra 3500HD IV, produced from 2015 to 2017, represents the fourth generation of GMC’s heavy-duty full-size pickup truck. Built on the GMTK2XX platform, this iteration of the Sierra 3500HD aimed to provide a robust and capable work truck while also offering increased refinement and technology compared to its predecessors. The Crew Cab Long Box configuration, paired with the 6.6-liter Duramax Turbo Diesel V8 engine producing 397 horsepower, was a popular choice for buyers needing substantial towing and hauling capacity combined with passenger space. This variant occupied a strong position in the lineup, appealing to both commercial users and individuals requiring a powerful and versatile truck.
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) SRW 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 | 8.4 kg/Hp, 119.7 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 312.7 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 | 3316 kg (7310.53 lbs.) |
| Max. weight | 5171 kg (11400.1 lbs.) |
| Max load | 1855 kg (4089.57 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.) |
| Ride height (ground clearance) | 214 mm (8.43 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 |
| 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 equipped with the 6.6-liter Duramax diesel and Allison automatic transmission was a cornerstone of GMC’s heavy-duty truck offerings. Positioned as a premium work truck, it catered to buyers who demanded substantial capability without sacrificing comfort or interior space. The “LML” Duramax engine, introduced in 2011, represented a significant evolution in diesel technology, focusing on increased efficiency and reduced emissions. The Crew Cab configuration provided ample room for passengers, making it suitable for both work crews and families. This model year range saw refinements to the GMTK2XX platform, enhancing ride quality and interior features.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the 6.6-liter Duramax LML turbo-diesel V8 engine. This engine utilizes a cast iron block and aluminum cylinder heads, contributing to its durability. The LML Duramax features a high-pressure common rail fuel injection system, capable of delivering fuel at over 30,000 psi for optimized combustion. The engine also incorporates a variable geometry turbocharger (VGT) and an intercooler to maximize power and efficiency. The valvetrain employs two valves per cylinder, operated by a pushrod (OHV) design, a traditional choice for diesel engines prioritizing robustness.
The Allison 1000 six-speed automatic transmission is specifically designed to handle the high torque output of the Duramax engine. This transmission features a lock-up torque converter for improved fuel economy and a heavy-duty cooling system to prevent overheating under demanding conditions. The Allison transmission is known for its durability and smooth shifting characteristics, making it a popular choice for heavy-duty applications. Gear ratios are optimized for both towing and everyday driving, providing a balance between power and efficiency.
Driving Characteristics
The 397 horsepower and 765 lb-ft of torque delivered by the Duramax engine and Allison transmission combination provide impressive performance. While not as quick off the line as gasoline-powered trucks, the Sierra 3500HD excels in situations requiring substantial pulling power. The Allison transmission shifts smoothly and efficiently, making it comfortable for both city and highway driving. The 6-speed automatic is well-matched to the engine’s torque curve, providing ample power in each gear. Compared to the 6.0L gasoline engine option, the Duramax offers significantly more torque at lower RPMs, making it ideal for towing heavy loads. Compared to higher-output Duramax variants, this 397 hp version offers a slightly more relaxed driving experience, prioritizing fuel economy and longevity over outright acceleration.
Equipment & Trim Levels
The Sierra 3500HD offered various trim levels, with the specific features varying depending on the chosen package. Generally, the Crew Cab Long Box 6.6L Duramax models came standard with features like air conditioning, power windows and locks, a tilt steering wheel, and a basic audio system. Higher trim levels, such as SLT and Denali, added features like leather upholstery, heated and ventilated seats, a premium audio system, navigation, and advanced safety technologies. Optional extras included a sunroof, 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 designed for strength and rigidity. 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, with larger rotors on the front axle. An Anti-lock Braking System (ABS) is standard. The rear axle configuration is Single Rear Wheel (SRW), suitable for most heavy-duty tasks. Stabilizer bars are included to reduce body roll during cornering.
Market Reception & Comparison
The GMC Sierra 3500HD with the Duramax diesel engine consistently received positive reviews for its towing capacity, durability, and comfortable ride. Critics praised the Allison transmission for its smooth shifting and reliability. Compared to competitors like the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as offering a more refined interior and a quieter cabin. Fuel economy, while not exceptional, was competitive for a heavy-duty diesel truck. The 397 hp Duramax variant offered a good balance between power and fuel efficiency, making it a popular choice for buyers who didn’t require the maximum towing capacity offered by higher-output engines.
Legacy
The Duramax LML engine and Allison transmission combination have proven to be exceptionally reliable, with many examples exceeding 200,000 miles with proper maintenance. The 2015-2017 Sierra 3500HD remains a sought-after truck in the used car market, particularly among buyers who need a capable and dependable work truck. Regular maintenance, including oil changes and fuel filter replacements, is crucial for ensuring the longevity of the Duramax engine. These trucks continue to hold their value well, reflecting their reputation for durability and capability. The GMTK2XX platform laid the groundwork for future generations of GMC heavy-duty trucks, continuing a legacy of robust and reliable performance.
