The GMC Sierra 2500HD IV (GMTK2XX) Double Cab Long Box, specifically equipped with the 6.0-liter V8 engine producing 301 horsepower and paired with an automatic transmission, and capable of running on Compressed Natural Gas (CNG), was a heavy-duty pickup truck produced by General Motors for the 2015 and 2016 model years. This variant occupied a significant position within the Sierra 2500HD lineup, offering a balance between capability, fuel efficiency (when utilizing CNG), and everyday usability for owners needing substantial towing and hauling capacity. It represented GMC’s commitment to providing professional-grade trucks for both commercial and personal use.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD IV (GMTK2XX) Double 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%) | 5897 kg / 13000.66 lbs. |
| Length | 6322 mm / 248.9 in. |
| Width including mirrors | 2045 mm / 80.51 in. |
| Height | 1978 mm / 77.87 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) | 216 mm / 8.5 in. |
| Minimum turning circle (turning diameter) | 16.2 m / 53.15 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 2015-2016 GMC Sierra 2500HD Double Cab Long Box with the 6.0L V8 and automatic transmission represented a workhorse offering in GMC’s heavy-duty truck lineup. Built on the GMTK2XX platform, this generation of Sierra 2500HD trucks aimed to provide increased capability, refinement, and technology compared to its predecessors. The availability of a CNG option broadened its appeal to fleet and environmentally conscious buyers. The Double Cab configuration offered a useful blend of passenger space and cargo bed length, making it suitable for both work and family needs. This particular variant, with its 301 horsepower and automatic transmission, was positioned as a strong all-around performer, capable of handling demanding tasks while providing a relatively comfortable driving experience.
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD variant lies the Vortec LC8 6.0-liter V8 engine. This engine is a naturally aspirated, overhead valve (OHV) design featuring variable valve timing (VVT) for improved efficiency and performance. The LC8 utilizes multi-port fuel injection to deliver fuel to the cylinders. The engine’s robust construction and large displacement provide ample torque for heavy hauling and towing. The 6.0L V8 produces 301 horsepower at 5000 rpm and 452 Nm (333.38 lb-ft) of torque at 4200 rpm. The engine’s internal components, including the cast iron block and aluminum cylinder heads, were designed for durability and longevity. The Hydra-Matic 6-speed automatic transmission was the sole transmission option for this configuration. This transmission is known for its smooth shifting and ability to handle the engine’s substantial torque output. The CNG system allows the truck to operate on either gasoline or compressed natural gas, offering potential cost savings and reduced emissions when CNG is readily available.
Driving Characteristics
The 6.0L V8 and 6-speed automatic combination in the Sierra 2500HD delivered a driving experience focused on capability and usability. While not as quick as some of the diesel-powered variants, the 301 horsepower engine provided sufficient power for most tasks. The automatic transmission offered smooth and predictable shifts, making it easy to drive in a variety of conditions. The gear ratios were optimized for towing and hauling, providing strong low-end torque. Compared to the more powerful diesel engines, this gasoline-powered version felt less stressed when towing near its maximum capacity. However, it also exhibited lower fuel economy, especially when not utilizing the CNG system. The ride quality, typical of a heavy-duty truck, was firm but reasonably comfortable, especially with the Double Cab configuration’s longer wheelbase.
Equipment & Trim Levels
The Sierra 2500HD Double Cab Long Box 6.0L CNG typically came standard with features such as air conditioning, power windows and locks, a basic audio system, and a tilt steering wheel. Higher trim levels, such as SLE and SLT, added features like leather upholstery, heated seats, a premium audio system, navigation, and a rearview camera. The Double Cab configuration provided seating for five passengers and a long bed for hauling cargo. Optional extras included a trailer brake controller, a locking rear differential, and various appearance packages. The interior design was functional and durable, with a focus on providing a comfortable and practical work environment.
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, while the rear suspension employed a traditional leaf spring setup. This configuration provided a good balance of ride comfort and load-carrying capacity. The braking system consisted of ventilated discs on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard equipment. The truck’s heavy-duty frame and suspension components contributed to its overall stability and durability. Steering was accomplished through a cone worm with recirculation balls system.
Market Reception & Comparison
The GMC Sierra 2500HD 6.0L CNG variant received generally positive reviews for its capability and versatility. Critics praised its strong engine, smooth transmission, and comfortable ride. However, some noted that its fuel economy was lower than that of the diesel-powered models. Compared to the 6.6L Duramax diesel, the 6.0L V8 offered a lower price point but less torque and towing capacity. The CNG option was seen as a positive feature for fleet operators and environmentally conscious buyers, but its practicality depended on the availability of CNG fueling stations. Against competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD offered a competitive combination of features, performance, and value.
Legacy
The 2015-2016 GMC Sierra 2500HD 6.0L V8 Automatic CNG remains a capable and reliable heavy-duty truck in the used car market. The Vortec LC8 engine is known for its durability, and the Hydra-Matic transmission is generally considered to be a robust unit. While maintenance costs may be higher than some newer trucks, the Sierra 2500HD offers a proven track record of dependability. The availability of the CNG option adds a unique appeal for those seeking alternative fuel solutions. These trucks continue to be popular choices for owners who need a powerful and versatile pickup for work or recreational purposes.
