The GMC Sierra 2500HD III, specifically the Crew 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 2013 and 2014. This variant represented a niche offering within the GMT900 platform – a facelift of the third-generation Sierra HD series – aimed at customers seeking heavy-duty capability with an alternative fuel option. It occupied a mid-range position in the 2500HD lineup, offering a balance between power, towing capacity, and the environmental benefits associated with CNG operation.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900, facelift 2011) Crew Cab Long Box |
| Type (Engine) | 6.0 V8 (301 Hp) Automatic CNG |
| Start of production | 2013 |
| End of production | 2014 |
| 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 |
| Length | 6581 mm / 259.09 in. |
| Width including mirrors | 2032 mm / 80 in. |
| Height | 1984 mm / 78.11 in. |
| Wheelbase | 4260 mm / 167.72 in. |
| Front track | 1748 mm / 68.82 in. |
| Rear (Back) track | 1709 mm / 67.28 in. |
| Ride height (ground clearance) | 211 mm / 8.31 in. |
| Minimum turning circle (turning diameter) | 16.7 m / 54.79 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 | 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 cubic inch) V8. This engine is a member of the Vortec family, known for its robust construction and relatively simple design. The LC8 utilizes an iron block with aluminum cylinder heads, and features a 9.6:1 compression ratio. Fuel delivery is managed by a multi-port fuel injection system, providing adequate atomization for efficient combustion. The overhead valve (OHV) valvetrain, while not as sophisticated as overhead cam designs, contributes to the engine’s durability and ease of maintenance. Variable Valve Timing (VVT) was incorporated to improve low-end torque and fuel efficiency. The engine produces 301 horsepower at 5000 rpm and 452 Nm (333.38 lb-ft) of torque at 4200 rpm.
The engine is mated to a 6-speed Hydra-Matic automatic transmission. This transmission was a common choice for GM trucks of this era, offering smooth shifting and reliable performance. The automatic transmission was particularly well-suited for heavy-duty applications, providing convenient operation when towing or hauling heavy loads. The CNG system is a bi-fuel setup, meaning the truck can run on either gasoline or CNG, or a combination of both. The CNG tank, with a capacity of 67 kg, is typically mounted in the bed of the truck, reducing cargo space.
Driving Characteristics
The 6.0L V8 with the 6-speed automatic provides adequate power for most heavy-duty tasks, but it’s not the most spirited performer in the Sierra 2500HD lineup. Compared to the available Duramax diesel engine, the gasoline V8 offers less low-end torque, requiring the transmission to downshift more frequently when towing or climbing hills. However, the V8 is quieter and smoother than the diesel, and it doesn’t suffer from the same diesel particulate filter (DPF) issues. The automatic transmission shifts smoothly and predictably, but it can sometimes feel hesitant when accelerating quickly. The CNG operation slightly reduces horsepower output compared to gasoline alone, but it also lowers emissions and can reduce fuel costs depending on CNG prices.
Equipment & Trim Levels
The CNG-capable Sierra 2500HD Crew Cab Long Box typically came equipped with a fairly comprehensive set of features. Standard equipment included air conditioning, power windows and locks, a basic audio system, and cloth upholstery. The Crew Cab configuration offered spacious seating for five passengers, making it a comfortable option for families or work crews. Optional extras included leather upholstery, a premium audio system, navigation, and various towing packages. The specific trim level (e.g., SLE, SLT) determined the level of standard equipment and available options.
Chassis & Braking
The Sierra 2500HD utilizes a body-on-frame construction, providing a robust and durable platform for heavy-duty applications. The front suspension consists of coil springs and a double wishbone setup, while the rear suspension employs a traditional leaf spring design. This configuration provides a comfortable ride while maintaining excellent load-carrying capacity. The braking system features ventilated discs on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. Steering is handled by a cone worm with recirculation balls system.
Market Reception & Comparison
The CNG-powered Sierra 2500HD was a relatively uncommon sight, as it catered to a specific niche of customers interested in alternative fuels. Critics generally praised the truck’s heavy-duty capability and comfortable ride, but noted that the CNG system reduced cargo space and slightly diminished performance. Compared to the gasoline-only version, the CNG model offered lower emissions and potentially lower fuel costs, but it also required access to a CNG refueling infrastructure. Compared to the diesel-powered Sierra 2500HD, the CNG model offered less torque and towing capacity, but it was quieter and simpler to maintain.
Legacy
The 2013-2014 GMC Sierra 2500HD CNG variant represents an interesting chapter in the evolution of heavy-duty trucks. While it didn’t achieve widespread popularity, it demonstrated GM’s commitment to exploring alternative fuel options. Today, these trucks can be found on the used car market, often at relatively affordable prices. The Vortec LC8 engine is known for its reliability, and the Hydra-Matic transmission is generally durable. However, potential buyers should be aware of the potential maintenance requirements associated with the CNG system, including periodic inspections and replacement of CNG system components. Overall, the Sierra 2500HD CNG remains a capable and practical truck for those seeking a heavy-duty vehicle with an alternative fuel option.
