The GMC Sierra 3500HD III, specifically the Crew Cab Long Box configuration with the 6.6-liter Duramax Turbo Diesel V8 engine and 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 aimed at buyers needing substantial towing and hauling capacity combined with a degree of interior comfort. It occupied a premium position within the Sierra 3500HD lineup, offering a powerful diesel option for demanding tasks. This model year saw refinements to the GMT900 platform, enhancing both its capabilities and refinement compared to earlier versions.
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) DRW 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 | 8.8 kg/Hp, 114.1 Hp/tonne |
| Weight-to-torque ratio | 3.4 kg/Nm, 298.1 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 | 3479 kg (7669.88 lbs.) |
| Max. weight | 5908 kg (13024.91 lbs.) |
| Max load | 2429 kg (5355.03 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%) | 7484 kg (16499.4 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 | 1906 mm (75.04 in.) |
| Ride height (ground clearance) | 216 mm (8.5 in.) |
| Minimum turning circle (turning diameter) | 16.9 m (55.45 ft.) |
| Drivetrain Architecture | Rear wheel drive |
| 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 is the 6.6-liter Duramax LML turbo diesel V8. 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 produces 397 horsepower at 3000 rpm and a substantial 765 lb-ft of torque at 1600 rpm. This torque output is crucial for heavy towing and hauling. The engine’s OHV valvetrain contributes to its durability and low-end grunt. Paired with the engine is the Allison 1000 six-speed automatic transmission, known for its durability and ability to handle high torque loads. This transmission features electronically controlled shifting and a lock-up torque converter for improved fuel efficiency.
Driving Characteristics
The 6.6L Duramax with the Allison automatic delivers a driving experience focused on capability rather than outright speed. While not a sports truck, the ample torque provides strong acceleration, even when heavily loaded. The Allison transmission shifts smoothly and predictably, and the gear ratios are well-suited for towing. Compared to the 6.0L gasoline V8 offered in the same generation, the Duramax provides significantly more torque at lower RPMs, making it far more capable for demanding tasks. The automatic transmission, while convenient, does result in a slight performance deficit compared to the available manual transmission, which allows for more direct control over gear selection. However, the automatic’s ease of use is a major benefit for drivers spending long hours in traffic or on the highway.
Equipment & Trim Levels
The Crew Cab Long Box configuration already denotes a higher level of trim, offering 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. The 2011-2013 facelift brought improvements to the interior materials and design. Optional extras included leather upholstery, a premium audio system, navigation, heated and cooled front seats, and a rear-seat entertainment system. The specific trim level (e.g., SLE, SLT) determined the standard equipment and available options. The DRW (Dual Rear Wheel) configuration was typically reserved for the highest towing capacities and often came with additional heavy-duty components.
Chassis & Braking
The Sierra 3500HD features a heavy-duty chassis designed to withstand significant loads. The front suspension utilizes an independent torsion bar setup with double wishbones, while the rear suspension employs a traditional leaf spring design. This combination provides a comfortable ride, even when the truck is unloaded, while maintaining excellent load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, with larger rotors on the front axle. An Anti-lock Braking System (ABS) is standard. The DRW configuration provides increased stability and braking power due to the wider stance and additional tires.
Market Reception & Comparison
The 2011-2013 GMC Sierra 3500HD with the Duramax diesel and Allison automatic was generally well-received by critics and consumers. It was praised for its powerful engine, smooth transmission, and comfortable ride. Fuel economy, while not exceptional, was considered reasonable for a heavy-duty truck of its size and capability. Compared to the Ford Super Duty and Ram 3500, the Sierra 3500HD offered a competitive combination of power, comfort, and features. The Duramax engine was often cited as a key advantage, offering a refined and powerful alternative to the gasoline engines offered by competitors.
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 trucks command a premium price due to their reputation for reliability and capability. The 2011-2013 model year represents a sweet spot in the GMT900 generation, offering the benefits of the facelifted design and the refined Duramax LML engine. These trucks remain popular choices for owners who need a powerful and dependable workhorse for towing, hauling, and everyday use.
