The GMC Sierra 3500HD III, specifically the facelifted model produced from 2011 to 2013, represented a significant iteration of GMC’s heavy-duty pickup truck lineage. Built on the GMT900 platform, this generation aimed to balance robust capability with improved refinement. The Extended Cab Long Box configuration, paired with the 6.6-liter Duramax turbodiesel V8 engine producing 397 horsepower and coupled to a 4WD Dual Rear Wheel (DRW) drivetrain with an Allison automatic transmission, positioned this truck as a workhorse for demanding tasks like heavy towing and hauling. This variant catered to professionals and enthusiasts requiring substantial payload and towing capacity without sacrificing everyday usability.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD III (GMT900, facelift 2011) Extended Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (397 Hp) 4WD DRW Automatic |
| Start of production | 2011 |
| End of production | 2013 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.8 kg/Hp, 113.4 Hp/tonne |
| Weight-to-torque ratio | 3.4 kg/Nm, 296.2 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 | 3501 kg (7718.38 lbs.) |
| Max. weight | 5908 kg (13024.91 lbs.) |
| Max load | 2407 kg (5306.53 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%) | 8165 kg (18000.74 lbs.) |
| Length | 6337 mm (249.49 in.) |
| Width including mirrors | 2436 mm (95.91 in.) |
| Height | 1966 mm (77.4 in.) |
| Wheelbase | 4018 mm (158.19 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1906 mm (75.04 in.) |
| Ride height (ground clearance) | 213 mm (8.39 in.) |
| Minimum turning circle (turning diameter) | 16.1 m (52.82 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, 355×40 mm |
| Rear brakes | Ventilated discs, 373×34 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 235/80 R17; 265/70 R18 |
Powertrain & Engine Architecture
The heart of this Sierra 3500HD variant is the 6.6-liter Duramax LML turbodiesel V8 engine. This engine represents a significant evolution of the Duramax design, incorporating a robust cast iron block, aluminum cylinder heads, and a high-pressure common rail fuel injection system. The LML specifically introduced a cooled exhaust gas recirculation (EGR) system and a diesel particulate filter (DPF) to meet stricter emissions standards. The engine’s 6.6-liter displacement, combined with a turbocharger and intercooler, allows it to produce 397 horsepower at 3000 rpm and a substantial 1037 Nm (764.85 lb-ft) of torque at just 1600 rpm. This torque output is crucial for heavy-duty applications. The engine utilizes an overhead valve (OHV) valvetrain, known for its durability and simplicity. The Allison 1000 six-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. It features a lock-up torque converter for improved fuel efficiency and a heavy-duty cooling system to prevent overheating under strenuous loads.
Driving Characteristics
The 6.6-liter Duramax with the Allison automatic delivers a driving experience focused on capability rather than outright speed. While not a sports truck, the abundant torque provides strong acceleration, even when heavily loaded. The Allison transmission is well-tuned for towing, offering smooth and predictable shifts. The gear ratios are optimized for pulling power, with a relatively low first gear for launching heavy loads. Compared to lighter-duty Sierra models or those equipped with gasoline engines, this variant feels substantial and planted. The Dual Rear Wheel configuration enhances stability, particularly when towing. Compared to the 1.8L gasoline engine options available in lighter duty Sierras, this Duramax offers a completely different experience, prioritizing pulling power and durability over fuel economy and nimble handling. The automatic transmission, while convenient, doesn’t offer the same level of control as a manual transmission, but it simplifies operation for drivers spending long hours in demanding conditions.
Equipment & Trim Levels
The 2011-2013 Sierra 3500HD Extended Cab Long Box with the Duramax engine typically came with a fairly comprehensive set of standard features, reflecting its positioning as a premium work truck. Standard equipment included air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. The Extended Cab provided additional rear seating, though legroom was limited. Optional extras included leather upholstery, a premium audio system, navigation, heated seats, and various towing packages. Trim levels varied, but generally included Work Truck (WT), LT, and SLT. The LT trim added features like chrome exterior trim, upgraded interior materials, and additional convenience features. The SLT trim represented the highest level of luxury, offering leather upholstery, premium audio, and a host of other amenities.
Chassis & Braking
The Sierra 3500HD’s chassis is built for heavy-duty use. It features a fully boxed frame constructed from high-strength steel. The front suspension utilizes an independent torsion bar setup with double wishbones, providing a comfortable ride while maintaining stability. The rear suspension employs a traditional leaf spring design, optimized for load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, with larger rotors at the rear (373×34 mm) to accommodate the increased weight. An Anti-lock Braking System (ABS) is standard. The DRW configuration significantly increases the truck’s stability and load-carrying capacity. Steering is accomplished via a cone worm and recirculation ball system, providing a robust and reliable feel.
Market Reception & Comparison
The 2011-2013 GMC Sierra 3500HD with the Duramax engine and Allison transmission was generally well-received by critics and consumers alike. It was praised for its immense towing and hauling capabilities, its comfortable ride (for a heavy-duty truck), and the reliability of the Duramax engine. Fuel economy, while not exceptional, was considered reasonable for a vehicle of this size and capability. Compared to the gasoline-powered Sierra 3500HD models, the Duramax offered significantly more torque and better fuel economy when towing heavy loads. Compared to competitors like the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as a strong contender, offering a compelling combination of power, refinement, and reliability.
Legacy
The Duramax LML engine paired with the Allison transmission has proven to be a remarkably durable and reliable powertrain. Properly maintained, these engines can easily exceed 200,000 miles. On the used car market, these Sierra 3500HD models hold their value well, particularly those in good condition with well-documented maintenance histories. The demand for capable heavy-duty trucks remains strong, and the 2011-2013 Sierra 3500HD continues to be a popular choice for those needing a robust and reliable workhorse. The LML Duramax engine is still considered one of the best diesel engines ever produced, and its reputation for longevity and performance continues to attract buyers today.
