The GMC Sierra 3500HD III, specifically the Crew Cab Long Box configuration with the 6.6-liter Duramax Turbo Diesel V8 engine paired with a 4WD SRW Automatic transmission, represents a significant iteration in GMC’s heavy-duty truck lineage. Produced from 2011 to 2013 as part of the GMT900 platform’s facelift, this variant was designed to cater to owners requiring substantial towing and hauling capabilities combined with a degree of passenger comfort. It occupied a premium position within the Sierra 3500HD lineup, offering a powerful diesel engine and four-wheel drive for demanding tasks.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD III (GMT900, facelift 2011) Crew Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (397 Hp) 4WD SRW Automatic |
| Start of production | 2011 |
| End of production | 2013 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.5 kg/Hp, 117.4 Hp/tonne |
| Weight-to-torque ratio | 3.3 kg/Nm, 306.6 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 | 3382 kg (7456.03 lbs.) |
| Max. weight | 5262 kg (11600.72 lbs.) |
| Max load | 1880 kg (4144.69 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 | 6581 mm (259.09 in.) |
| Width including mirrors | 2436 mm (95.91 in.) |
| Height | 1979 mm (77.91 in.) |
| Wheelbase | 4260 mm (167.72 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Ride height (ground clearance) | 213 mm (8.39 in.) |
| Minimum turning circle (turning diameter) | 16.7 m (54.79 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 |
INTRODUCTION
The 2011-2013 GMC Sierra 3500HD Crew Cab Long Box with the 6.6L Duramax diesel and Allison automatic transmission represented a sweet spot for buyers needing serious capability. Positioned as a premium offering within the 3500HD range, it catered to those who frequently towed large trailers – boats, RVs, or construction equipment – while still desiring a comfortable and spacious cabin for passengers. This generation benefited from a mid-cycle refresh (facelift) in 2011, bringing updated styling and improved interior materials. It built upon the foundation of the GMT900 platform, shared with Chevrolet Silverado HD models, but distinguished itself with GMC’s unique styling cues and generally more upscale appointments.
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the Duramax LML 6.6-liter turbocharged diesel V8. This engine, a significant evolution of the previous LBZ and LMM Duramax engines, produced 397 horsepower at 3000 rpm and a massive 765 lb-ft (1037 Nm) of torque at 1600 rpm. The LML featured a redesigned combustion chamber, improved fuel injectors, and a more efficient turbocharger. The fuel system utilized a common-rail direct injection system, delivering highly pressurized fuel for optimal combustion. The engine employed an overhead valve (OHV) valvetrain, a design choice favored for its durability and low-end torque characteristics. Paired with the Duramax was the Allison 1000 six-speed automatic transmission, renowned for its robustness and ability to handle the engine’s substantial torque output. This transmission featured a lock-up torque converter for improved fuel efficiency at highway speeds and was specifically calibrated for heavy-duty applications.
Driving Characteristics
The combination of the Duramax diesel and Allison automatic resulted in a truck that felt incredibly capable and composed, even when heavily loaded. The 6-speed Allison transmission provided smooth and decisive shifts, and the torque converter lock-up helped maintain reasonable fuel economy during highway cruising. While not a sports truck, the Sierra 3500HD offered ample power for merging onto highways and passing slower vehicles. The 4WD system provided excellent traction in various conditions, making it suitable for both on-road and off-road use. Compared to the gasoline-powered Sierra 3500HD models, the diesel offered significantly more torque, making it far superior for towing and hauling. Compared to earlier Duramax engines, the LML offered improved refinement and reduced noise, vibration, and harshness (NVH).
Equipment & Trim Levels
The Crew Cab Long Box configuration offered a spacious interior with seating for five passengers. Standard features typically included air conditioning, power windows and locks, a tilt steering wheel, and a basic audio system. Higher trim levels, such as SLT and Denali, added features like leather upholstery, heated and cooled front seats, a premium audio system, navigation, and a rear-seat entertainment system. The interior design was functional and durable, with a focus on providing a comfortable and practical environment for both work and family use. Optional extras included a sunroof, upgraded wheels, and various towing packages.
Chassis & Braking
The Sierra 3500HD 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, while the rear suspension employed a traditional leaf spring design. This configuration provided a good balance of ride comfort and load-carrying capacity. Braking duties were handled by ventilated disc brakes at all four corners, providing ample stopping power even when towing a heavy load. An Anti-lock Braking System (ABS) was standard. The rear axle was a single rear wheel (SRW) configuration, common for this class of truck.
Market Reception & Comparison
The 2011-2013 GMC Sierra 3500HD with the Duramax diesel and Allison automatic received generally positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, comfortable ride, and spacious interior. Fuel economy, while not exceptional, was considered reasonable for a heavy-duty truck of its size and capability. Compared to the gasoline-powered Sierra 3500HD models, the diesel offered significantly better fuel economy when towing. The Duramax/Allison combination was often seen as the benchmark in the heavy-duty truck segment, competing directly with Ford’s Power Stroke diesel and Ram’s Cummins diesel engines.
Legacy
The Duramax LML engine and Allison 1000 transmission have proven to be exceptionally durable and reliable powertrains. Well-maintained examples of the 2011-2013 Sierra 3500HD continue to command strong resale values in the used car market. The LML Duramax is known for its longevity and relatively low maintenance costs, making it a popular choice among truck enthusiasts and commercial users. While some early LML engines experienced issues with the exhaust gas recirculation (EGR) system, these problems were largely addressed through software updates and improved components. Today, this Sierra 3500HD remains a capable and dependable workhorse, representing a high point in GMC’s heavy-duty truck history.
