The GMC Sierra 3500HD IV (GMTK2XX) Crew Cab Long Box, specifically equipped with the 6.0-liter V8 engine producing 301 horsepower and paired with a 4WD automatic transmission, and capable of running on Compressed Natural Gas (CNG), was produced for the 2015 and 2016 model years. This variant represented a heavy-duty pickup truck option aimed at buyers needing substantial towing and payload capacity, with the added flexibility of alternative fuel operation. It falls within the fourth generation of the Sierra 3500HD line, built on the GMTK2XX platform, which brought significant improvements in capability, refinement, and technology compared to its predecessors.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD IV (GMTK2XX) Crew Cab Long Box |
| Type (Engine) | 6.0 V8 (301 Hp) 4WD Automatic CNG |
| Start of production | 2015 |
| End of production | 2016 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Petrol / CNG |
| Power | 301 Hp @ 5000 rpm |
| Power per litre | 50.4 Hp/l |
| Torque | 452 Nm @ 4200 rpm / 333.38 lb.-ft. @ 4200 rpm |
| Maximum engine speed | 6000 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Vortec LC8 |
| Engine displacement | 5967 cm3 / 364.13 cu. in. |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 101.6 mm / 4 in. |
| Piston Stroke | 92 mm / 3.62 in. |
| Compression ratio | 9.6:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | OHV, VVT |
| Engine oil capacity | 5.7 l / 6.02 US qt | 5.02 UK qt |
| Coolant | 15.5 l / 16.38 US qt | 13.64 UK qt |
| Fuel tank capacity | 136 l / 35.93 US gal | 29.92 UK gal |
| CNG cylinder capacity | 67 kg |
| Permitted trailer load with brakes (12%) | 3856 kg / 8501.02 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. |
| Ride height (ground clearance) | 218 mm / 8.58 in. |
| Minimum turning circle (turning diameter) | 17.1 m / 56.1 ft. |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels permanently, and the front wheels are driven through an electrically or mechanically operated clutch if necessary. |
| Drive wheel | All wheel drive (4×4) |
| Number of gears and type of gearbox | 6 gears, automatic transmission Hydra-Matic |
| Front suspension | Coil spring, Double wishbone, Transverse stabilizer |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 350×40 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 |
Powertrain & Engine Architecture
At the heart of this Sierra 3500HD variant lies the Vortec LC8 engine, a 6.0-liter (364 cubic inch) V8. This engine is a member of the Vortec family, known for its robust construction and relatively simple design. It features a cast iron block and aluminum cylinder heads. The LC8 utilizes a multi-port fuel injection system, delivering fuel to each cylinder individually for optimized combustion. The overhead valve (OHV) valvetrain, while traditional, is paired with variable valve timing (VVT) to improve efficiency and low-end torque. The engine’s 9.6:1 compression ratio strikes a balance between power and durability. The 4L80-E Hydra-Matic automatic transmission, a four-speed unit, was the standard pairing. This transmission is known for its durability and ability to handle the high torque output of the 6.0L V8, making it well-suited for heavy-duty applications. The addition of CNG capability involved a dedicated fuel system alongside the gasoline system, allowing the truck to switch between fuels or operate on a blend.
Driving Characteristics
The 301 horsepower and 333 lb-ft of torque provided by the 6.0L V8 and 4L80-E transmission combination delivered adequate, but not exceptional, performance for a heavy-duty truck. Acceleration was brisk enough for everyday driving, but the truck’s substantial weight limited its responsiveness. The four-speed automatic transmission, while reliable, lacked the gear ratios found in more modern transmissions, resulting in slightly higher engine speeds at highway cruising. Compared to the available 6.6L Duramax diesel engine, this gasoline-powered variant offered significantly less torque and towing capacity. However, it was quieter and smoother than the diesel, and the CNG option provided potential cost savings for operators with access to affordable CNG fuel. The 4WD system provided enhanced traction in challenging conditions, making it suitable for both work and recreational use.
Equipment & Trim Levels
The Sierra 3500HD Crew Cab Long Box with the 6.0L V8 and CNG option typically came well-equipped, though specific features varied depending on the chosen trim level (SLE or SLT). Standard features generally included air conditioning, power windows and locks, a basic audio system, and cloth upholstery. The Crew Cab configuration offered spacious seating for five passengers. Optional extras included leather upholstery, a premium audio system, navigation, a rearview camera, and various towing packages. The SLT trim added more luxurious appointments, such as heated seats and upgraded interior trim.
Chassis & Braking
The GMTK2XX platform featured a fully boxed frame for enhanced rigidity and durability. The front suspension utilized a coil spring, double wishbone design with a transverse stabilizer bar, while the rear suspension employed a traditional leaf spring setup. This configuration prioritized load-carrying capacity and stability. Brakes consisted of ventilated discs at all four corners, providing adequate stopping power for the truck’s weight. An Anti-lock Braking System (ABS) was standard. The rear axle ratios were selected to optimize towing performance and fuel economy, depending on the specific configuration.
Market Reception & Comparison
The 6.0L V8/4WD/CNG Sierra 3500HD was a niche offering within the Sierra lineup. Critics generally praised its robust construction and towing capability, but noted that it lacked the sheer power and efficiency of the Duramax diesel engine. The CNG option was seen as a positive for environmentally conscious buyers and those seeking to reduce fuel costs, but its practicality depended on the availability of CNG refueling stations. Compared to competitors like the Ford Super Duty and Ram 3500, the Sierra 3500HD offered a competitive combination of features and capability, but often came at a higher price point.
Legacy
The Vortec LC8 engine, while not as technologically advanced as some of its competitors, proved to be a reliable and durable powerplant. The 4L80-E transmission is also known for its longevity. Today, used examples of the 2015-2016 Sierra 3500HD with this powertrain configuration are relatively common and can be found at reasonable prices. However, potential buyers should be aware of the potential maintenance costs associated with a high-mileage truck, including the CNG system. The combination of gasoline/CNG flexibility and heavy-duty capability continues to appeal to a segment of the market seeking a versatile and capable work truck.
