The GMC Sierra 2500HD III, specifically the Extended Cab Standard 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 heavy-duty pickup truck designed for demanding work and towing applications. It aimed to provide a balance between capability, fuel flexibility, and a more accessible price point compared to the diesel-powered options available in the Sierra 2500HD lineup.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900, facelift 2011) Extended Cab Standard 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 | 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 |
| Length | 5857 mm / 230.59 in. |
| Width including mirrors | 2032 mm / 80 in. |
| Height | 1979 mm / 77.91 in. |
| Wheelbase | 3663 mm / 144.21 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) | 14.6 m / 47.9 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 |
INTRODUCTION
The 2013-2014 GMC Sierra 2500HD Extended Cab Standard Box 6.0L V8 Automatic CNG represented a specific configuration within the third generation of the Sierra 2500HD (GMT900 platform). The GMT900 series, introduced in 2007 and receiving a facelift in 2011, was GMC’s offering in the heavy-duty pickup truck segment, competing with Ford’s Super Duty and Ram’s 2500/3500 series. The Extended Cab provided additional passenger space compared to the regular cab models, while the Standard Box offered a practical bed length for hauling. The inclusion of CNG capability was relatively uncommon, targeting fleet and commercial customers seeking alternative fuel options.
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD was the Vortec LC8 6.0-liter V8 engine. This engine, a staple in GM’s truck lineup for many years, is a naturally aspirated, overhead valve (OHV) design featuring variable valve timing (VVT) on intake valves. The LC8 utilized a cast iron block and aluminum cylinder heads. Fuel delivery was handled by a multi-port fuel injection system. The engine produced 301 horsepower at 5000 rpm and 360 lb-ft of torque at 4200 rpm. The CNG system was a bi-fuel setup, allowing the truck to run on either gasoline or compressed natural gas, or a combination of both.
The engine was mated to a six-speed Hydra-Matic automatic transmission. This transmission was known for its durability and smooth shifting characteristics. The gear ratios were optimized for towing and hauling, with a relatively deep first gear for launching heavy loads and overdrive gears for efficient highway cruising. The automatic transmission was a key component in making the truck accessible to a wider range of drivers who preferred the convenience of an automatic over a manual transmission.
Driving Characteristics
The 6.0L V8 Automatic combination delivered a noticeable balance between power and usability. While not as potent as the available Duramax diesel engine, the 6.0L provided ample torque for most everyday hauling tasks and towing needs. The automatic transmission contributed to a smooth and predictable driving experience. Compared to manual transmission equipped models, the automatic offered less driver involvement but greater ease of use, particularly in stop-and-go traffic. The CNG system, when utilized, slightly reduced overall power output compared to gasoline-only operation, but offered potential cost savings depending on CNG fuel prices.
Equipment & Trim Levels
The 2500HD offered a range of trim levels, and the 6.0L CNG variant was typically available in work truck (WT) and SLE trims. The WT trim was the base model, focusing on functionality and affordability. Standard features included air conditioning, a basic audio system, and vinyl upholstery. The SLE trim added more comfort and convenience features, such as cloth upholstery, power windows and locks, and an upgraded audio system. Optional extras included a navigation system, leather upholstery, and a premium sound system. The CNG system itself was often a factory-installed option, integrated seamlessly into the vehicle’s fuel system.
Chassis & Braking
The Sierra 2500HD featured a robust chassis designed to handle heavy loads. The front suspension utilized coil springs and a double wishbone design with a transverse stabilizer bar. The rear suspension employed a traditional leaf spring setup, providing a high load-carrying capacity. Braking duties were handled by ventilated disc brakes on all four wheels. An Anti-lock Braking System (ABS) was standard equipment. The rear axle ratios varied depending on the specific configuration, influencing both towing capacity and fuel economy.
Market Reception & Comparison
The 6.0L V8 Automatic CNG Sierra 2500HD received mixed reviews. Critics acknowledged its capability and the benefits of CNG as an alternative fuel, but often pointed to the lower power output compared to the diesel options. Fuel economy was generally considered adequate, but not exceptional. Compared to the 6.6L Duramax diesel, the 6.0L offered a lower initial purchase price but significantly less towing capacity and fuel efficiency. The CNG variant appealed to a specific segment of buyers – those prioritizing fuel cost savings and environmental considerations over outright performance.
Legacy
The 2013-2014 GMC Sierra 2500HD 6.0L V8 Automatic CNG, while a relatively short-lived configuration, represents an interesting chapter in the evolution of heavy-duty trucks. The Vortec LC8 engine, while not the most technologically advanced, proved to be a reliable and durable powerplant. The Hydra-Matic transmission also enjoyed a good reputation for longevity. On the used car market, these trucks are often sought after by those looking for a capable and affordable work truck, particularly in areas with readily available CNG infrastructure. The CNG system, if properly maintained, can offer significant fuel cost savings, making these trucks an attractive option for fleet operators and individuals alike.
