The Chevrolet Silverado 3500 HD II (GMT900) Extended Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 365 horsepower and paired with an Allison automatic transmission, represents a significant iteration in Chevrolet’s heavy-duty truck lineage. Produced from 2007 to 2010, this variant occupied a crucial position in the American truck market, catering to buyers needing substantial towing and hauling capabilities without sacrificing everyday usability. It was part of the GMT900 series, a generation known for its increased interior space, improved ride quality, and enhanced powertrain options compared to its predecessors.
Technical Specifications
| Brand | Chevrolet |
| Model | Silverado 3500 HD |
| Generation | Silverado 3500 HD II (GMT900) Extended Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (365 Hp) SRW Automatic |
| Start of production | 2007 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.2 kg/Hp, 122.4 Hp/tonne |
| Weight-to-torque ratio | 3.3 kg/Nm, 300 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 | 2983 kg (6576.39 lbs.) |
| Max. weight | 4400 kg (9700.34 lbs.) |
| Max load | 1417 kg (3123.95 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 | 6330 mm (249.21 in.) |
| Width including mirrors | 2436 mm (95.91 in.) |
| Height | 1931 mm (76.02 in.) |
| Wheelbase | 4001 mm (157.52 in.) |
| Front track | 1742 mm (68.58 in.) |
| Rear (Back) track | 1676 mm (65.98 in.) |
| Ride height (ground clearance) | 233 mm (9.17 in.) |
| Minimum turning circle (turning diameter) | 16 m (52.49 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, 325×38 mm |
| Rear brakes | Ventilated discs, 325×30 mm |
| Tires size | 265/75 R16; 225/75 R17 |
| Wheel rims size | 7J x 16; 7.5J x 17 |
INTRODUCTION
The 2007-2010 Chevrolet Silverado 3500 HD II, specifically the Extended Cab Long Box configuration with the 6.6L Duramax diesel and Allison automatic, was a workhorse designed for demanding tasks. This generation (GMT900) represented a significant step forward for Chevrolet’s heavy-duty trucks, offering a more refined interior, improved ride quality, and increased capability. The Extended Cab provided additional passenger space, making it suitable for both work and family use, while the Long Box offered ample cargo capacity. This particular variant was positioned as a mid-to-high range offering, appealing to customers who required serious towing and hauling power but didn’t necessarily need the highest trim levels.
Powertrain & Engine Architecture
At the heart of this Silverado 3500 HD lies the Duramax LMM 6.6-liter turbocharged diesel V8 engine. This engine is a testament to diesel engineering, featuring a cast iron block, aluminum cylinder heads, and a robust crankshaft. The LMM engine built upon the foundation of the previous LBZ Duramax, incorporating a more effective exhaust gas recirculation (EGR) system and a diesel particulate filter (DPF) to meet stricter emissions standards. The common-rail fuel injection system, delivering fuel at extremely high pressures, ensures efficient combustion and optimal power output. The overhead valve (OHV) valvetrain, while seemingly traditional, proved reliable and contributed to the engine’s low-end torque characteristics. The Allison 1000 series 6-speed automatic transmission is renowned for its durability and ability to handle the immense torque produced by the Duramax engine. It features electronically controlled shifting and a lock-up torque converter for improved fuel efficiency.
Driving Characteristics
The Silverado 3500 HD with the 6.6L Duramax and Allison automatic delivers a driving experience focused on capability and control. While not a sports truck, the 365 horsepower and 895 lb-ft of torque provide ample power for towing heavy loads and accelerating with authority. The Allison transmission’s gear ratios are optimized for both towing and highway cruising. The automatic transmission, while convenient, does result in a slight reduction in fuel economy compared to a manual transmission. However, the smooth and predictable shifting of the Allison more than compensates for this in many applications. Compared to the gasoline-powered Silverado 3500 HD models, the Duramax diesel offers significantly more torque at lower RPMs, making it ideal for hauling and towing. The ride quality, while firm due to the heavy-duty suspension, is surprisingly comfortable, especially considering the truck’s intended purpose.
Equipment & Trim Levels
The Extended Cab Long Box 3500 HD typically came standard with features like air conditioning, power windows and locks, and a basic audio system. The interior upholstery was typically cloth, although leather options were available. The dashboard layout was functional and straightforward, prioritizing ease of use over flashy aesthetics. Optional extras included a premium audio system, navigation system, heated seats, and a power sunroof. Trim levels varied, with the LT and LTZ trims offering more luxurious appointments and features. The LT trim added features like chrome exterior trim, upgraded interior materials, and additional convenience features, while the LTZ trim represented the pinnacle of luxury for the Silverado 3500 HD.
Chassis & Braking
The Silverado 3500 HD’s chassis is built for strength and durability. The front suspension utilizes an independent torsion bar setup with double wishbones, providing a comfortable ride and good handling. The rear suspension employs a traditional leaf spring design, optimized for carrying heavy loads. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) is standard, enhancing safety and control during emergency braking situations. The truck’s robust frame and heavy-duty components contribute to its impressive towing and payload capacity.
Market Reception & Comparison
The 2007-2010 Silverado 3500 HD with the Duramax diesel and Allison automatic was generally well-received by critics and consumers alike. It was praised for its powerful engine, smooth transmission, and comfortable ride. Compared to its competitors, such as the Ford Super Duty and Ram Heavy Duty, the Silverado 3500 HD offered a compelling combination of capability, comfort, and value. Fuel economy, while not exceptional, was competitive for a heavy-duty truck. Reliability was generally good, although some owners reported issues with the diesel particulate filter (DPF) system. The Duramax/Allison combination proved to be exceptionally durable, with many trucks exceeding 200,000 miles with proper maintenance.
Legacy
The Duramax LMM engine and Allison transmission combination found in the 2007-2010 Silverado 3500 HD remains highly regarded in the used truck market. These trucks are known for their longevity and ability to handle demanding tasks. While maintenance costs can be higher than gasoline-powered trucks, the Duramax engine’s fuel efficiency and long lifespan often offset these costs. The LMM Duramax is considered by many to be one of the most reliable and durable diesel engines ever produced. Today, these trucks continue to be popular choices for those needing a capable and reliable heavy-duty work truck.
