The GMC Sierra 2500HD IV (GMTK2XX) Double Cab Long Box, equipped with the 6.0-liter V8 engine producing 301 horsepower and running on a combination of petrol and Compressed Natural Gas (CNG), was a heavy-duty pickup truck produced for the 2015 and 2016 model years. This variant occupied a significant position within the fourth generation of the Sierra 2500HD lineup, catering to buyers needing substantial towing and hauling capacity with an alternative fuel option. It represented GMC’s commitment to providing robust work trucks with increasing fuel flexibility, appealing to both commercial and private users.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD IV (GMTK2XX) Double 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%) | 5897 kg / 13000.66 lbs. |
| Length | 6322 mm / 248.9 in. |
| Width including mirrors | 2045 mm / 80.51 in. |
| Height | 1977 mm / 77.83 in. |
| Wheelbase | 4017 mm / 158.15 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) | 16.2 m / 53.15 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, 360×34 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 245/75 R17; 265/70 R17; 265/70 R18; 265/60 R20 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 20 |
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD variant lies the Vortec LC8 engine, a 6.0-liter (364.13 cubic inches) V8. This engine is characterized by its cast iron block and aluminum cylinder heads, a design choice prioritizing durability and cost-effectiveness. The LC8 utilizes a traditional overhead valve (OHV) valvetrain with variable valve timing (VVT) on intake valves, enhancing low-end torque and improving fuel efficiency. Fuel delivery is managed by a multi-port fuel injection system. The engine’s 9.6:1 compression ratio contributes to its robust power output. The addition of a CNG system allows for bi-fuel operation, reducing reliance on gasoline and potentially lowering emissions. The Hydra-Matic 6-speed automatic transmission was the sole transmission option, chosen for its durability and ability to handle the engine’s torque output. This transmission features electronically controlled shifting and overdrive for improved highway fuel economy.
Driving Characteristics
The 301 horsepower and 333.38 lb-ft of torque provided by the 6.0L V8 and automatic transmission combination delivered adequate, though 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 automatic transmission’s gear ratios were optimized for towing and hauling, prioritizing low-end grunt over outright speed. Compared to the available diesel engines in the Sierra 2500HD lineup, this gasoline/CNG variant offered less torque, making it less ideal for extremely heavy loads. However, it provided a smoother and quieter driving experience than the diesel options. The 4WD system provided enhanced traction in challenging conditions, making it suitable for both on- and off-road use.
Equipment & Trim Levels
The Double Cab Long Box configuration offered a spacious interior with seating for five passengers. Standard features typically included air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. Higher trim levels, such as the SLT and Denali, added features like leather upholstery, heated seats, a premium audio system, and advanced safety technologies. The CNG system was typically an optional upgrade, adding a dedicated CNG fuel tank and fuel delivery system. Exterior features included a chrome grille, body-color bumpers, and standard halogen headlights. Optional equipment included a trailer brake controller, a navigation system, and a sunroof.
Chassis & Braking
The Sierra 2500HD IV utilized a body-on-frame construction, providing a robust and durable platform for heavy-duty applications. The front suspension featured 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 ride comfort. 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. The truck’s substantial weight and high center of gravity necessitated a robust braking system and careful driving habits.
Market Reception & Comparison
The 6.0L V8/Automatic/CNG Sierra 2500HD received mixed reviews. Critics praised its comfortable ride and spacious interior, but noted its lower towing capacity and fuel economy compared to the diesel-powered models. The CNG option was seen as a positive step towards alternative fuels, but its limited refueling infrastructure was a drawback. Compared to the 6.6L Duramax diesel engine, the 6.0L V8 offered significantly less torque and fuel efficiency, but it was also less expensive to purchase and maintain. The gasoline/CNG variant appealed to buyers who prioritized affordability and a smoother driving experience over maximum towing capacity.
Legacy
The GMC Sierra 2500HD IV (GMTK2XX) with the 6.0L V8 and CNG option represents a transitional period in the heavy-duty truck market. While diesel engines remained the dominant choice for serious towing and hauling, this variant offered a viable alternative for buyers seeking a more affordable and environmentally conscious option. The Vortec LC8 engine, while not known for exceptional fuel economy, proved to be a reliable and durable powerplant. Today, these trucks can be found on the used car market at relatively affordable prices, making them an attractive option for buyers seeking a capable and dependable work truck. However, potential buyers should be aware of the potential maintenance costs associated with an older vehicle and the limited availability of CNG refueling stations.
