The GMC Sierra 2500HD III, specifically the facelifted model produced from 2011 to 2014, represented a significant evolution in GMC’s heavy-duty truck lineup. This variant, featuring an Extended Cab with a Long Box, coupled with the 6.6-liter Duramax Turbo Diesel V8 engine producing 397 horsepower and paired with a 4WD automatic transmission, was positioned as a workhorse for those needing substantial towing and hauling capacity. Built on the GMT900 platform, it catered to buyers requiring a robust and capable truck for both commercial and personal use, particularly in markets where heavy-duty pickups were in high demand.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900, facelift 2011) Extended Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (397 Hp) 4WD Automatic |
| Start of production | 2011 |
| End of production | 2014 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.3 kg/Hp, 120.3 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 314.2 Nm/tonne |
| Power | 397 Hp @ 3000 rpm |
| Power per litre | 60.2 Hp/l |
| Torque | 1037 Nm @ 1600 rpm (764.85 lb.-ft. @ 1600 rpm) |
| Maximum engine speed | 3000 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax LML |
| Engine displacement | 6599 cm3 (402.7 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 103 mm (4.06 in.) |
| Piston Stroke | 99 mm (3.9 in.) |
| Compression ratio | 16:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | OHV |
| Engine oil capacity | 9.5 l (10.04 US qt | 8.36 UK qt) |
| Coolant | 24 l (25.36 US qt | 21.12 UK qt) |
| Kerb Weight | 3300 kg (7275.25 lbs.) |
| Max. weight | 4536 kg (10000.17 lbs.) |
| Max load | 1236 kg (2724.91 lbs.) |
| Trunk (boot) space – maximum | 2138 l (75.5 cu. ft.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 5897 kg (13000.66 lbs.) |
| Length | 6337 mm (249.49 in.) |
| Width including mirrors | 2032 mm (80 in.) |
| Height | 1971 mm (77.6 in.) |
| Wheelbase | 4018 mm (158.19 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) | 15.8 m (51.84 ft.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front wheels engaged via clutch. |
| Number of gears and type of gearbox | 6 gears, automatic transmission Allison |
| Front suspension | Independent torsion bar, double wishbone |
| 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
The heart of this Sierra 2500HD was the Duramax LML 6.6-liter turbocharged diesel V8. This engine represented a significant upgrade over previous Duramax iterations, incorporating a redesigned combustion chamber, improved fuel injection system, and a more robust cooling system. The LML utilized a common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion efficiency and reduced emissions. The engine featured an overhead valve (OHV) valvetrain, a design choice favored for its durability and low-end torque characteristics. The turbocharger and intercooler worked in tandem to increase air density, further enhancing power output. The Allison 6-speed automatic transmission was specifically calibrated to handle the immense torque produced by the Duramax engine, providing smooth and reliable shifting even under heavy loads.
Driving Characteristics
The 397 horsepower and 765 lb-ft of torque delivered by the Duramax engine and Allison transmission combination resulted in impressive performance. While not designed for outright speed, this Sierra 2500HD excelled at towing and hauling. The automatic transmission, while smooth, was tuned for functionality rather than sportiness. Gear ratios were optimized for maximizing torque at lower RPMs, making it ideal for pulling heavy trailers or navigating challenging terrain. Compared to the gasoline-powered versions of the Sierra 2500HD, the diesel offered significantly more low-end grunt and superior fuel economy when towing. The 4WD system provided enhanced traction in slippery conditions, making it a capable off-road performer as well.
Equipment & Trim Levels
The 2011-2014 Sierra 2500HD with the Duramax engine and automatic transmission typically came well-equipped, though specific features varied depending on the chosen trim level. Standard features generally included air conditioning, power windows and locks, a basic audio system, and a tilt steering wheel. Higher trim levels, such as the SLT and Denali, added features like leather upholstery, heated seats, a premium audio system, navigation, and a rear vision camera. Optional extras included a sunroof, upgraded wheels, and various towing packages. The Extended Cab configuration provided additional passenger space compared to the regular cab models, making it a more comfortable option for families or crews.
Chassis & Braking
The Sierra 2500HD’s chassis was built for durability and heavy-duty use. It featured a fully boxed frame constructed from high-strength steel. The front suspension utilized an independent torsion bar setup with double wishbones, providing a comfortable ride while maintaining stability. The rear suspension employed a traditional leaf spring design, capable of handling substantial payloads. 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 during emergency braking situations. The heavy-duty suspension components and robust braking system were essential for managing the truck’s considerable weight and towing capacity.
Market Reception & Comparison
The 2011-2014 GMC Sierra 2500HD with the Duramax diesel and automatic transmission was generally well-received by critics and consumers alike. It was praised for its powerful engine, impressive towing capacity, and comfortable ride. Fuel economy, while not exceptional, was considered good for a heavy-duty truck. Compared to the gasoline-powered Sierra 2500HD models, the diesel variant commanded a higher price but offered superior performance and efficiency when used for demanding tasks. Competitors like the Ford Super Duty and Ram 2500/3500 offered similar capabilities, but the Sierra 2500HD consistently ranked among the top contenders in the heavy-duty truck segment.
Legacy
The Duramax LML engine paired with the Allison automatic transmission has proven to be a remarkably reliable powertrain. Properly maintained examples of the 2011-2014 Sierra 2500HD continue to command strong resale values in the used car market. The engine is known for its longevity and ability to withstand high mileage. While some maintenance items, such as the diesel particulate filter, can be costly to repair, the overall reliability of this powertrain has solidified its reputation as a workhorse. These trucks remain popular choices for those needing a capable and dependable heavy-duty pickup for work or recreational purposes.
