The GMC Sierra 3500HD III, specifically the facelifted model produced from 2011 to 2014, 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 Regular Cab Long Box configuration, paired with the 6.6-liter Duramax turbodiesel V8 engine producing 397 horsepower and a substantial 1037 Nm (764.85 lb-ft) of torque, and a six-speed Allison automatic transmission, was a popular choice for those needing serious towing and hauling capacity. This particular variant occupied a strong position within the Sierra 3500HD lineup, appealing to commercial users and private owners alike who demanded uncompromising performance.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD III (GMT900, facelift 2011) Regular Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (397 Hp) 4WD DRW 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 | 8.3 kg/Hp, 120.2 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 313.9 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 | 3304 kg (7284.07 lbs.) |
| Max. weight | 5908 kg (13024.91 lbs.) |
| Max load | 2604 kg (5740.84 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%) | 7258 kg (16001.15 lbs.) |
| Length | 5715 mm (225 in.) |
| Width including mirrors | 2436 mm (95.91 in.) |
| Height | 1966 mm (77.4 in.) |
| Wheelbase | 3369 mm (132.64 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1906 mm (75.04 in.) |
| Ride height (ground clearance) | 218 mm (8.58 in.) |
| Minimum turning circle (turning diameter) | 13.9 m (45.6 ft.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front wheels engaged via clutch. |
| Drive wheel | All wheel drive (4×4) |
| 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 |
INTRODUCTION
The 2011-2014 GMC Sierra 3500HD Regular Cab Long Box with the 6.6L Duramax diesel and Allison automatic was a workhorse designed for demanding tasks. Positioned as a heavy-duty offering within the broader Sierra lineup, it catered to buyers needing substantial towing and payload capabilities. The facelift introduced in 2011 brought updated styling, improved interior materials, and enhanced features compared to the previous GMT900 generation. This model year marked a significant step forward in terms of both capability and refinement for GMC’s heavy-duty trucks, solidifying its position in the competitive American pickup truck market.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax LML 6.6-liter V8 turbodiesel engine. This engine, a staple of GMC and Chevrolet heavy-duty trucks, utilizes a cast iron block and aluminum cylinder heads. The LML generation introduced a revised combustion chamber and a cooled exhaust gas recirculation (EGR) system to further reduce emissions. Fuel is delivered via a high-pressure common rail diesel injection system, ensuring precise fuel metering for optimal combustion and efficiency. The engine features an overhead valve (OHV) valvetrain, known for its durability and simplicity. A variable geometry turbocharger and intercooler work in tandem to maximize power and torque across the engine’s operating range. The Allison 1000 six-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. This transmission features a lock-up torque converter for improved fuel economy and a heavy-duty cooling system to prevent overheating under strenuous conditions.
Driving Characteristics
The combination of the 397-hp Duramax engine and the Allison automatic transmission delivers a commanding driving experience. While not as quick off the line as gasoline-powered trucks, the Sierra 3500HD excels in situations requiring substantial pulling power. The Allison transmission’s gear ratios are optimized for towing, providing ample torque in lower gears and efficient cruising in higher gears. Compared to the 6.0L gasoline V8 option, the Duramax offers significantly more torque, making it the preferred choice for heavy hauling. The automatic transmission, while smooth and reliable, doesn’t offer the same level of driver engagement as a manual transmission. However, it simplifies operation, especially in stop-and-go traffic or when towing heavy loads. The dual rear wheel (DRW) configuration enhances stability when towing and increases payload capacity.
Equipment & Trim Levels
The Regular Cab Long Box configuration typically came with a relatively basic level of standard equipment, focusing on functionality and durability. Standard features included air conditioning, a basic audio system, and vinyl upholstery. However, buyers could opt for a range of optional extras, including power windows and locks, a premium audio system, leather upholstery, and a navigation system. Trim levels varied, with the base model offering minimal frills, while higher trims added more comfort and convenience features. The interior design was functional and straightforward, prioritizing ease of use and durability over luxury.
Chassis & Braking
The Sierra 3500HD’s chassis is built for heavy-duty use. It features a fully boxed frame constructed from high-strength steel, providing a solid foundation for the truck’s components. The front suspension utilizes an independent torsion bar setup with double wishbone control arms, offering a comfortable ride and good handling. The rear suspension employs a traditional leaf spring design, optimized for load-carrying capacity. Braking duties are handled by ventilated disc brakes at all four corners, providing ample stopping power even when towing heavy loads. An Anti-lock Braking System (ABS) is standard, enhancing safety and control. The DRW configuration provides increased stability and braking performance.
Market Reception & Comparison
The 2011-2014 GMC Sierra 3500HD with the Duramax diesel and Allison automatic received generally positive reviews from automotive critics. It was praised for its robust towing and hauling capabilities, comfortable ride, and refined interior (especially in higher trim levels). Compared to the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as offering a good balance of capability, comfort, and value. Fuel economy, while respectable for a heavy-duty truck, was not a primary selling point. Reliability was generally good, although some owners reported issues with the diesel particulate filter (DPF) system.
Legacy
The Duramax LML engine and Allison transmission pairing in the 2011-2014 GMC Sierra 3500HD has proven to be a durable and reliable powertrain. These trucks continue to be popular on the used car market, commanding relatively high prices due to their proven capabilities. The LML Duramax is known for its longevity and relatively low maintenance costs, making it a desirable engine for buyers seeking a long-lasting work truck. While newer heavy-duty trucks offer more advanced technology and features, the GMT900-based Sierra 3500HD remains a capable and dependable option for those needing a robust and reliable pickup truck.
