The GMC Sierra 2500HD III, specifically the Crew Cab Standard Box configuration with the 6.6-liter Duramax Turbo Diesel V8 engine and four-wheel drive automatic transmission, represents a significant iteration in GMC’s heavy-duty truck lineup. Produced from 2011 to 2014 as part of the GMT900 platform’s facelift, this variant was designed to balance robust towing capability with a degree of everyday usability. It occupied a sweet spot in the Sierra 2500HD range, appealing to owners needing serious work capacity without necessarily opting for the extreme capabilities of the 3500HD models.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD III (GMT900, facelift 2011) Crew Cab Standard 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 | 5 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.3 kg/Hp, 120 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 313.5 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 | 3308 kg (7292.89 lbs.) |
| Max. weight | 4536 kg (10000.17 lbs.) |
| Max load | 1228 kg (2707.28 lbs.) |
| Trunk (boot) space – maximum | 1718 l (60.67 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 | 6101 mm (240.2 in.) |
| Width including mirrors | 2032 mm (80 in.) |
| Height | 1958 mm (77.09 in.) |
| Wheelbase | 3904 mm (153.7 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Ride height (ground clearance) | 208 mm (8.19 in.) |
| Minimum turning circle (turning diameter) | 15.4 m (50.52 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 is the Duramax LML 6.6-liter turbocharged diesel V8. This engine represented a significant evolution of the Duramax design, 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’s OHV valvetrain, while traditional, was optimized for low-end torque. The turbocharger and intercooler work in tandem to increase air density, boosting power output. The Allison 6-speed automatic transmission was specifically calibrated to handle the immense torque produced by the Duramax engine. This transmission featured a lock-up torque converter for improved fuel efficiency at highway speeds and heavy-duty internal components for durability.
Driving Characteristics
The 397 horsepower and 765 lb-ft of torque delivered by this combination resulted in impressive towing and hauling capabilities. While not as quick as lighter-duty trucks, the Sierra 2500HD offered strong acceleration, even when heavily loaded. The Allison transmission provided smooth and predictable shifts, although some drivers noted a slight delay in downshifts when compared to manual transmission equipped models. The gear ratios were optimized for towing, prioritizing low-end grunt over outright speed. Compared to the gasoline-powered 6.0L V8 option, the Duramax diesel offered significantly more torque, making it the preferred choice for those regularly towing heavy trailers or hauling substantial payloads. The automatic transmission, while convenient, did slightly diminish fuel economy compared to the available manual transmission.
Equipment & Trim Levels
The Crew Cab Standard Box configuration offered a spacious interior with seating for five passengers. Standard features typically included air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. Higher trim levels, such as the SLT and Denali, added features like leather upholstery, heated seats, a premium audio system, navigation, and a rear-seat entertainment system. Optional extras included a sunroof, upgraded wheels, and various towing packages. The standard box length provided a good balance between cargo capacity and overall vehicle length.
Chassis & Braking
The Sierra 2500HD featured a robust chassis designed to withstand the stresses of heavy-duty use. The front suspension utilized an independent torsion bar setup with double wishbones, providing a comfortable ride while maintaining good handling characteristics. The rear suspension employed a traditional leaf spring design, optimized for load-carrying capacity. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard equipment. The heavy-duty suspension and braking system were crucial for safely managing the truck’s substantial weight and towing capacity.
Market Reception & Comparison
The 2011-2014 GMC Sierra 2500HD with the Duramax diesel and Allison automatic received generally positive reviews. Critics praised its powerful engine, smooth transmission, and comfortable ride. Fuel economy, while not exceptional, was considered reasonable for a heavy-duty truck. Compared to the Ford Super Duty and Ram 2500/3500, the Sierra 2500HD was often seen as offering a more refined interior and a quieter cabin. However, some reviewers noted that the GMC’s price was slightly higher than its competitors. The Duramax/Allison combination was consistently lauded for its reliability and longevity.
Legacy
The Duramax LML engine and Allison transmission pairing have proven to be exceptionally durable and reliable. Well-maintained examples of this Sierra 2500HD continue to command strong resale values in the used car market. The engine is known for its ability to accumulate high mileage with minimal issues, provided regular maintenance is performed. The GMT900 platform, while superseded by newer generations, remains a popular choice for those seeking a capable and dependable heavy-duty truck. The 2011-2014 facelifted models, in particular, are often sought after for their improved features and refined styling.
