The GMC Sierra 3500HD III, produced from 2007 to 2010, represented a significant evolution in GMC’s heavy-duty truck lineup. Part of the GMT900 generation, this iteration of the Sierra 3500HD was designed to cater to the demands of serious work and towing. The Crew Cab Long Box configuration, paired with the 6.6-liter Duramax Turbo Diesel V8 engine producing 365 horsepower, and a six-speed Allison automatic transmission, was a popular choice for those needing substantial capability and interior space. This particular variant, often referred to as a “dually” due to its dual rear wheels, positioned itself as a premium offering within the 3500HD range, aimed at customers requiring maximum towing and payload capacity.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD III (GMT900) Crew Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (365 Hp) DRW Automatic |
| Start of production | 2007 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.3 kg/Hp, 120.5 Hp/tonne |
| Weight-to-torque ratio | 3.4 kg/Nm, 295.5 Nm/tonne |
| Power | 365 Hp @ 3200 rpm |
| Power per litre | 55.3 Hp/l |
| Torque | 895 Nm @ 1600 rpm (660.12 lb.-ft. @ 1600 rpm) |
| Maximum engine speed | 3450 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax LMM |
| 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 | 16.8:1 |
| 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 | 3029 kg (6677.8 lbs.) |
| Max. weight | 4445 kg (9799.55 lbs.) |
| Max load | 1416 kg (3121.75 lbs.) |
| Trunk (boot) space – maximum | 2170 l (76.63 cu. ft.) |
| Fuel tank capacity | 129 l (34.08 US gal | 28.38 UK gal) |
| Permitted trailer load with brakes (12%) | 5897 kg (13000.66 lbs.) |
| Length | 6572 mm (258.74 in.) |
| Width including mirrors | 2436 mm (95.91 in.) |
| Height | 1931 mm (76.02 in.) |
| Wheelbase | 4242 mm (167.01 in.) |
| Front track | 1742 mm (68.58 in.) |
| Rear (Back) track | 1897 mm (74.69 in.) |
| Ride height (ground clearance) | 233 mm (9.17 in.) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | 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, 325×38 mm |
| Rear brakes | Ventilated discs, 325×30 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 265/75 R16; 265/70 R17; 225/75 R17 |
| Wheel rims size | 6.5J x 17; 7J x 16; 7.5J x 17 |
Powertrain & Engine Architecture
The heart of this Sierra 3500HD variant is the Duramax LMM 6.6-liter turbocharged diesel V8. This engine, a product of a joint venture between General Motors and Isuzu, was a significant upgrade over its predecessor, the LBZ. The LMM featured a redesigned combustion chamber and improved fuel injection system, contributing to increased power and reduced emissions. The engine utilizes a common-rail direct injection system, delivering fuel at extremely high pressures for optimal combustion. The valvetrain employs an overhead valve (OHV) configuration, known for its simplicity and durability. The Duramax engine is longitudinally mounted in the chassis. Paired with the engine is the Allison 1000 six-speed automatic transmission, renowned for its robustness and ability to handle high torque loads. This transmission was specifically designed for heavy-duty applications and featured a lock-up torque converter for improved fuel efficiency.
Driving Characteristics
The 365 horsepower and 895 lb-ft of torque delivered by the Duramax/Allison combination provided substantial performance, even when heavily loaded. While not designed for outright speed, the Sierra 3500HD offered strong acceleration and effortless towing capability. The six-speed automatic transmission allowed for relatively tight gear ratios, keeping the engine in its optimal power band. Compared to the 1.8L gasoline engine options available in lighter-duty Sierra models, this diesel offered a vastly different driving experience – prioritizing torque and towing capacity over fuel economy and nimble handling. The dually rear wheel setup provided enhanced stability when towing heavy loads, minimizing sway and improving overall control. The ride quality, while firm, was acceptable for a heavy-duty truck, and the Allison transmission provided smooth and predictable shifts.
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 CD player, and cloth upholstery. Higher trim levels, such as the LT and LTZ, added features like leather upholstery, heated seats, a premium sound system, and navigation. Optional extras included a sunroof, remote start, and various towing packages. The interior design was functional and durable, reflecting the truck’s work-oriented purpose. The dashboard layout was straightforward and easy to use, with large, clearly marked controls.
Chassis & Braking
The Sierra 3500HD III featured a robust chassis designed to withstand heavy loads and demanding conditions. The front suspension utilized an independent torsion bar setup with double wishbones, providing a comfortable ride and good handling. The rear suspension employed a traditional leaf spring design, optimized for load-carrying capacity. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard equipment. The dually rear wheel configuration significantly increased the truck’s braking capacity and stability when towing.
Market Reception & Comparison
The GMC Sierra 3500HD III with the Duramax diesel and Allison automatic received generally positive reviews. Critics praised its powerful engine, smooth transmission, and impressive towing capacity. Fuel economy, while not exceptional, was considered reasonable for a truck of its size and capability. Compared to other heavy-duty trucks in its class, such as the Ford Super Duty and Ram 3500, the Sierra 3500HD was often seen as a well-rounded and reliable option. The Duramax engine was particularly well-regarded for its longevity and relatively low maintenance costs.
Legacy
The GMT900 generation Sierra 3500HD, and particularly the 6.6L Duramax/Allison combination, has proven to be a durable and reliable powertrain. These trucks remain popular in the used market, often commanding premium prices due to their reputation for longevity and capability. The LMM Duramax engine is generally considered to be one of the most reliable Duramax engines produced, with many examples exceeding 200,000 miles with proper maintenance. Regular maintenance, including oil changes and fuel filter replacements, is crucial for ensuring the long-term health of the engine and transmission. Today, these trucks continue to be used for a variety of applications, including hauling, towing, and commercial work.
