The GMC Sierra 2500HD III, specifically the facelifted model produced from 2011 to 2014, represented a significant iteration in GMC’s heavy-duty truck lineup. This variant, configured with a Regular Cab, Long Box, and powered by the 6.6-liter Duramax turbodiesel V8 engine producing 397 horsepower, coupled with a 4WD system and automatic transmission, was a workhorse designed for demanding tasks. It sat within the GMT900 platform generation, offering a balance of capability, comfort, and technology for the American truck buyer. This configuration was positioned as a robust, capable option for those needing serious towing and hauling capacity, but perhaps not requiring the added space or luxury of crew cab models.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900, facelift 2011) Regular 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 | 2 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.8 kg/Hp, 128.3 Hp/tonne |
| Weight-to-torque ratio | 3 kg/Nm, 335.2 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 | 3094 kg (6821.1 lbs.) |
| Max. weight | 4491 kg (9900.96 lbs.) |
| Max load | 1397 kg (3079.86 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 | 5715 mm (225 in.) |
| Width including mirrors | 2032 mm (80 in.) |
| Height | 1971 mm (77.6 in.) |
| Wheelbase | 3369 mm (132.64 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Ride height (ground clearance) | 231 mm (9.09 in.) |
| Minimum turning circle (turning diameter) | 13.7 m (44.95 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 V8 turbodiesel. This engine represented a significant evolution of the Duramax design, incorporating a redesigned combustion chamber, improved fuel injection system, and a more efficient turbocharger. The LML utilized a common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion. 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, boosting power and efficiency. The Allison 6-speed automatic transmission was specifically calibrated to handle the immense torque output of the Duramax engine. This transmission was known for its robustness and smooth shifting, crucial for heavy-duty applications.
Driving Characteristics
The 397 horsepower and 765 lb-ft of torque delivered by the Duramax engine, combined with the Allison automatic, provided substantial pulling power. While not as quick as gasoline-powered trucks, the 2500HD excelled at towing and hauling heavy loads. The automatic transmission, while smooth, was tuned for work rather than sport, prioritizing consistent power delivery over rapid acceleration. The gear ratios were optimized for maintaining engine RPMs within the peak torque band, ensuring strong performance even when fully loaded. Compared to the 6.0L gasoline V8 option, the Duramax offered significantly more torque and better fuel economy, albeit at a higher initial cost. Compared to other Duramax configurations, like those with manual transmissions, the automatic offered ease of use, particularly in stop-and-go traffic or challenging terrain.
Equipment & Trim Levels
The Regular Cab Long Box 2500HD typically came with a relatively basic level of standard equipment, focusing on functionality. Standard features included air conditioning, a basic audio system, and vinyl upholstery. However, options were plentiful. Buyers could add features like power windows and locks, upgraded audio systems, leather upholstery, and a navigation system. The interior was designed with durability in mind, featuring robust materials and a straightforward layout. Trim levels varied, but generally offered increasing levels of comfort and convenience features.
Chassis & Braking
The Sierra 2500HD’s chassis was built for heavy-duty use. It featured a fully boxed frame for increased rigidity and strength. 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.
Market Reception & Comparison
The 2011-2014 GMC Sierra 2500HD with the Duramax engine and automatic transmission was well-received by truck enthusiasts and professionals alike. Critics praised its robust powertrain, impressive towing capacity, and comfortable ride. Fuel economy, while not exceptional, was considered good for a heavy-duty truck. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD offered a compelling combination of power, refinement, and value. The Duramax/Allison combination was often cited as a key advantage, offering a smooth and reliable powertrain.
Legacy
The Duramax LML engine and Allison automatic transmission have proven to be remarkably durable and reliable powertrains. Well-maintained examples of the 2011-2014 Sierra 2500HD continue to command strong resale values in the used truck market. The engine is known for its longevity, with many units exceeding 200,000 miles with proper maintenance. While diesel engines can be more expensive to repair than gasoline engines, the Duramax’s reputation for reliability makes it a desirable choice for buyers seeking a long-lasting and capable work truck. The GMT900 platform, and this specific configuration, remains a popular choice for those needing a heavy-duty truck that can handle demanding tasks for years to come.
