The GMC Sierra 3500HD IV, specifically the Crew Cab Long Box configuration with the 6.0-liter V8 engine paired to an 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 (GMTK2XX) of the Sierra 3500HD line, known for its increased strength and refinement compared to previous generations. This particular trim level positioned itself as a work-focused, yet comfortably equipped, option within the Sierra 3500HD range.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD IV (GMTK2XX) Crew Cab Long Box |
| Type (Engine) | 6.0 V8 (301 Hp) 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%) | 4037 kg / 8900.06 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 | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| 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, coupled with variable valve timing (VVT), helps to balance power delivery and fuel efficiency. The engine is designed to run on gasoline, but this specific configuration was also equipped to operate on Compressed Natural Gas (CNG), offering an alternative fuel source. The Hydra-Matic 6L90 six-speed automatic transmission was the sole transmission option, providing smooth shifting and adequate gear ratios for heavy hauling.
Driving Characteristics
The 301 horsepower and 333 lb-ft of torque produced by the 6.0L V8, while substantial, were not the highest figures available in the Sierra 3500HD lineup. Compared to the available Duramax diesel engine, this gasoline V8 offered less low-end torque, making it feel less effortless when towing extremely heavy loads. However, the gasoline engine provided a more familiar driving experience for many drivers, with a quicker throttle response and a more traditional engine sound. The six-speed automatic transmission was well-matched to the engine’s powerband, providing adequate gear ratios for both highway cruising and hauling. The automatic transmission, while convenient, did result in a slight reduction in fuel economy compared to the available manual transmission options.
Equipment & Trim Levels
The Crew Cab Long Box 6.0L CNG variant typically came standard with features expected of a heavy-duty pickup, including air conditioning, power windows and locks, and a basic audio system. The Crew Cab configuration offered spacious seating for five passengers, making it suitable for both work and family use. Higher trim levels added features such as leather upholstery, heated seats, a premium audio system, and navigation. The CNG system itself was a significant addition, requiring dedicated fuel tanks and fuel lines, and often included a switch to select between gasoline and CNG operation.
Chassis & Braking
The Sierra 3500HD featured a fully boxed frame designed for maximum strength and rigidity. The front suspension utilized a coil spring, double wishbone setup with a transverse stabilizer bar, while the rear suspension employed a traditional leaf spring design. This configuration provided a comfortable ride, even when carrying heavy loads. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard, enhancing safety and control during emergency braking situations.
Market Reception & Comparison
The 6.0L V8/automatic CNG Sierra 3500HD was generally well-received by buyers seeking a gasoline-powered, heavy-duty truck with the added benefit of alternative fuel capability. Critics noted the engine’s adequate power and smooth operation, but also pointed out its lower fuel economy compared to the diesel option. The CNG system was seen as a positive for environmentally conscious buyers and those looking to reduce their fuel costs, particularly in areas where CNG was readily available and competitively priced. Compared to the diesel-powered Sierra 3500HD, this variant was typically less expensive to purchase, but offered less towing capacity and fuel efficiency.
Legacy
The GMTK2XX Sierra 3500HD, including the 6.0L V8 CNG variant, has proven to be a durable and reliable truck. The Vortec LC8 engine, while not as fuel-efficient as modern engines, is known for its longevity and relatively simple maintenance requirements. The Hydra-Matic transmission is also generally considered to be a reliable unit. On the used car market, these trucks remain popular among buyers seeking a capable and affordable heavy-duty pickup. The CNG system, while requiring specialized maintenance, can still provide significant fuel savings for owners who have access to CNG fueling stations. Overall, the 2015-2016 GMC Sierra 3500HD 6.0L V8 CNG represents a solid and dependable work truck with a unique alternative fuel option.
