The GMC Sierra 3500HD IV, specifically the Regular Cab Long Box configuration with the 6.0L V8 engine paired to an automatic transmission and capable of running on Compressed Natural Gas (CNG), was produced for a limited run between 2015 and 2016. This variant represented a niche offering within the fourth generation (GMTK2XX) Sierra 3500HD lineup, aimed at fleet and commercial customers seeking a heavy-duty pickup with alternative fuel capabilities. It occupied a position between the standard gasoline-powered models and the diesel-powered options, offering a balance of power, towing capacity, and reduced emissions when operating on CNG.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD IV (GMTK2XX) Regular 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 | 2 |
| Doors | 2 |
| 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%) | 4264 kg / 9400.51 lbs. |
| Length | 5699 mm / 224.37 in. |
| Width including mirrors | 2035 mm / 80.12 in. |
| Height | 1977 mm / 77.83 in. |
| Wheelbase | 3393 mm / 133.58 in. |
| Front track | 1748 mm / 68.82 in. |
| Rear (Back) track | 1709 mm / 67.28 in. |
| Ride height (ground clearance) | 229 mm / 9.02 in. |
| Minimum turning circle (turning diameter) | 14 m / 45.93 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, 360×34 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 6.0-liter V8 engine. This engine, a staple of GM’s heavy-duty truck lineup for many years, is a naturally aspirated, overhead valve (OHV) design featuring variable valve timing (VVT). The LC8 utilizes multi-port fuel injection to deliver fuel to the cylinders. The engine produces 301 horsepower at 5000 rpm and 452 Nm (333.38 lb-ft) of torque at 4200 rpm. The engine’s robust construction and relatively simple design contribute to its reputation for reliability. The automatic transmission used is the Hydra-Matic 6-speed automatic, known for its durability and smooth shifting characteristics. The addition of a CNG system allows the truck to operate on either gasoline or compressed natural gas, or a combination of both, reducing reliance on gasoline and lowering emissions when running on CNG.
Driving Characteristics
The 6.0L V8 with the Hydra-Matic automatic provides adequate power for most heavy-duty tasks, but it doesn’t offer the same level of performance as the available diesel engines. Acceleration is moderate, and the truck feels less responsive than its diesel counterparts. The automatic transmission is well-matched to the engine’s torque curve, providing smooth and predictable gear changes. The gear ratios are optimized for towing and hauling, prioritizing low-end torque over outright speed. When operating on CNG, a slight reduction in power output can be expected, but the difference is generally not significant for typical work applications. The long wheelbase of the Regular Cab Long Box configuration contributes to a comfortable ride, but it also makes the truck less maneuverable in tight spaces.
Equipment & Trim Levels
The 2015-2016 Sierra 3500HD Regular Cab Long Box 6.0L CNG typically came with a base level of equipment focused on functionality and durability. Standard features included air conditioning, a basic audio system, vinyl upholstery, and manual windows and locks. The interior was designed with work in mind, prioritizing ease of cleaning and durability over luxury. Optional extras included power windows and locks, upgraded audio systems, and various towing packages. The CNG system itself was a significant addition, often specified by fleet operators to take advantage of CNG fuel infrastructure and incentives.
Chassis & Braking
The Sierra 3500HD features a heavy-duty chassis designed to withstand the stresses of towing and hauling. The front suspension utilizes coil springs and a double wishbone design with a transverse stabilizer bar, while the rear suspension employs a traditional leaf spring setup. This configuration provides a good balance of ride comfort and load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when heavily loaded. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations.
Market Reception & Comparison
The Sierra 3500HD 6.0L CNG variant received mixed reviews. Critics acknowledged the benefits of the CNG system in terms of reduced emissions and fuel costs (where CNG was cheaper than gasoline), but noted the limited availability of CNG fueling stations and the potential for reduced power output when running on CNG. Compared to the diesel-powered Sierra 3500HD models, the 6.0L CNG offered less towing capacity and lower fuel economy. However, it was generally more affordable to purchase and maintain than the diesel options. The 6.0L gasoline engine was seen as a good option for those who didn’t require the ultimate in towing performance but still needed a capable heavy-duty truck.
Legacy
The GMC Sierra 3500HD 6.0L CNG represents a relatively uncommon variant within the GMTK2XX generation. While not a high-volume seller, it served a specific niche in the market, providing a heavy-duty truck option for customers seeking alternative fuel capabilities. The Vortec LC8 engine is known for its durability and relatively simple maintenance requirements, making these trucks a potentially reliable choice in the used car market. However, the CNG system itself may require periodic maintenance and inspection to ensure proper operation. Today, these trucks are often found in the hands of fleet operators or individuals who have access to CNG fueling infrastructure.
