The GMC Sierra 3500HD III, specifically the facelifted model produced from 2011 to 2014, represented GMC’s heavy-duty pickup truck offering within the GMT900 platform generation. This variant, configured as a Regular Cab with a Long Box, and powered by the 6.6-liter Duramax turbodiesel V8 engine paired with a 4WD SRW (Single Rear Wheel) automatic transmission, was aimed at buyers needing substantial towing and hauling capacity. It occupied a position in the lineup geared towards professional use and demanding workloads, bridging the gap between the lighter-duty Sierra 1500 and the even more capable Sierra 4500HD.
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 SRW 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 | 7 kg/Hp, 143.7 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 375.3 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 | 2763 kg (6091.37 lbs.) |
| Max. weight | 4854 kg (10701.24 lbs.) |
| Max load | 2091 kg (4609.87 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 | 5715 mm (225 in.) |
| Width including mirrors | 2032 mm (80 in.) |
| Height | 1971 mm (77.6 in.) |
| Wheelbase | 3369 mm (132.64 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Ride height (ground clearance) | 218 mm (8.58 in.) |
| Minimum turning circle (turning diameter) | 13.7 m (44.95 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 Duramax LML 6.6-liter turbodiesel V8 engine. This engine, a significant evolution of the Duramax design, features a cast iron block and aluminum cylinder heads. The LML introduced a revised combustion chamber, a cooled exhaust gas recirculation (EGR) system, and a more efficient turbocharger. The engine utilizes a high-pressure common rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The overhead valve (OHV) valvetrain, while traditional, is robust and well-suited to the demands of heavy-duty operation. The Allison 6-speed automatic transmission is a key component, specifically tuned to handle the engine’s substantial torque output. This transmission features a lock-up torque converter for improved fuel efficiency at highway speeds and is known for its durability.
Driving Characteristics
The 397 horsepower and 765 lb-ft of torque delivered by the Duramax engine provide substantial pulling power. While not designed for rapid acceleration, this configuration excels at towing and hauling heavy loads. The Allison automatic transmission provides smooth shifts, although it may exhibit some hunting for the optimal gear when under heavy load. Compared to the gasoline-powered Sierra 3500HD models, the diesel offers significantly more low-end torque, making it ideal for tasks like construction, farming, and long-distance towing. The 4WD system provides enhanced traction in challenging conditions, but the vehicle’s substantial weight impacts handling and maneuverability.
Equipment & Trim Levels
The Regular Cab Long Box configuration typically represented a work-oriented trim level. Standard features generally included air conditioning, a basic audio system, vinyl upholstery, and manually adjustable seats. Optional extras could include power windows and locks, upgraded audio systems, a trailer brake controller, and various towing packages. Interior appointments were functional rather than luxurious, prioritizing durability and ease of cleaning. The exterior typically featured black plastic trim and steel wheels, although chrome packages were available as options.
Chassis & Braking
The Sierra 3500HD’s chassis is built around a heavy-duty frame designed to withstand significant stress. The front suspension utilizes an independent torsion bar setup with double wishbones, providing a relatively comfortable ride despite the truck’s weight. 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, with ABS as standard equipment. The rear brakes are slightly smaller in diameter than the front brakes, reflecting the weight distribution of the vehicle.
Market Reception & Comparison
The 2011-2014 GMC Sierra 3500HD with the Duramax diesel and Allison automatic received generally positive reviews. Critics praised its towing and hauling capabilities, as well as the Duramax engine’s reliability and fuel efficiency (for a heavy-duty diesel). Compared to the 6.0L gasoline V8 option, the Duramax offered significantly better fuel economy and torque. However, the diesel engine carried a higher price tag and potentially higher maintenance costs. Compared to competitors like the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as a well-rounded and capable offering.
Legacy
The Duramax LML engine, as found in this Sierra 3500HD, has proven to be a durable and reliable powertrain. Well-maintained examples continue to command strong resale values in the used truck market. The Allison transmission is also highly regarded for its longevity. Common maintenance items include regular oil changes, fuel filter replacements, and coolant flushes. While diesel engines generally require more expensive maintenance than gasoline engines, the Duramax LML has earned a reputation for being a robust and long-lasting powerplant, making this particular Sierra 3500HD variant a desirable choice for buyers seeking a capable and dependable heavy-duty truck.
