The Chevrolet Silverado 3500 HD IV (T1XX) Double Cab Long Bed, equipped with the 6.6-liter Duramax V8 engine producing 445 horsepower and paired with an Allison 10-speed automatic transmission, represents a significant iteration in Chevrolet’s heavy-duty truck lineage. Produced from 2020 through 2023, this configuration occupied a premium position within the Silverado 3500 HD lineup, targeting buyers requiring substantial towing and hauling capabilities without sacrificing everyday usability. It built upon the foundation of the T1XX platform, introduced with the 2020 model year, offering enhanced strength, technology, and refinement compared to its predecessors.
Technical Specifications
| Brand | Chevrolet |
| Model | Silverado 3500 HD |
| Generation | Silverado 3500 HD IV (T1XX) Double Cab Long Bed |
| Type (Engine) | 6.6 Duramax V8 (445 Hp) SRW Automatic |
| Start of production | 2020 |
| End of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.8 kg/Hp, 127.7 Hp/tonne |
| Weight-to-torque ratio | 2.8 kg/Nm, 354.1 Nm/tonne |
| Power | 445 Hp @ 2800 rpm |
| Power per litre | 67.4 Hp/l |
| Torque | 1234 Nm @ 1600 rpm (910.15 lb.-ft. @ 1600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | Duramax L5P |
| Engine displacement | 6604 cm3 (403 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 | 29.1 l (30.75 US qt | 25.6 UK qt) |
| Kerb Weight | 3485 kg (7683.11 lbs.) |
| Max. weight | 5375 kg (11849.85 lbs.) |
| Max load | 1890 kg (4166.74 lbs.) |
| Trunk (boot) space – maximum | 2364 l (83.48 cu. ft.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 9747 kg (21488.46 lbs.) |
| Length | 6514 mm (256.46 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2054 mm (80.87 in.) |
| Wheelbase | 4127 mm (162.48 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 284 mm (11.18 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine. |
| Number of gears and type of gearbox | 10 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, 360×34 mm |
| Tires size | 265/70 R17; 245/75 R17; 265/70 R18 |
| Wheel rims size | 7.5J x 17; 8J x 18 |
INTRODUCTION
The 2020-2023 Chevrolet Silverado 3500 HD Double Cab Long Bed with the 6.6L Duramax diesel and Allison automatic transmission was positioned as a workhorse for serious towing and hauling. It represented the fourth generation of the Silverado HD series (T1XX platform), designed to offer increased capability and a more refined driving experience. The Double Cab configuration provided a balance between passenger space and bed length, making it suitable for both work and family needs. This particular variant was a step up from the base gasoline engine options, appealing to customers who frequently tow large trailers, such as fifth-wheels, gooseneck trailers, or heavy equipment.
Powertrain & Engine Architecture
At the heart of this Silverado 3500 HD lies the Duramax L5P 6.6-liter V8 diesel engine. This engine is a turbocharged, overhead valve (OHV) design, known for its robust construction and longevity. The L5P utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for efficient combustion. A variable geometry turbocharger (VGT) and intercooler work in tandem to maximize power and torque across a broad RPM range. The engine produces 445 horsepower at 2800 rpm and a substantial 910 lb-ft (1234 Nm) of torque at 1600 rpm.
The Allison 10-speed automatic transmission is a crucial component of this powertrain. This transmission is specifically designed to handle the high torque output of the Duramax engine and provide smooth, efficient shifting. The ten forward gears allow for optimized engine RPMs in various driving conditions, improving both fuel economy and towing performance. The transmission features electronically controlled shifting and a tow/haul mode that adjusts shift points for optimal towing control.
Driving Characteristics
The Silverado 3500 HD with this powertrain delivers a commanding driving experience. The abundant torque is readily available, providing effortless acceleration even when heavily loaded. While not a sports truck, the 10-speed Allison transmission keeps the engine in its optimal power band, resulting in confident passing maneuvers. Compared to the 6.0L gasoline V8, the Duramax diesel offers significantly more torque, making it far superior for towing. Compared to the 6.6L Duramax in earlier generations, the 10-speed Allison provides a wider gear ratio spread, improving both fuel economy and towing stability. The ride quality, even unladen, is surprisingly comfortable for a heavy-duty truck, thanks to the refined suspension tuning.
Equipment & Trim Levels
The Silverado 3500 HD Double Cab Long Bed with the Duramax/Allison combination typically came in higher trim levels, such as LT, LTZ, and High Country. Standard features included air conditioning, power windows and locks, a touchscreen infotainment system with Apple CarPlay and Android Auto compatibility, and a rearview camera. Higher trims added features like leather upholstery, heated and ventilated front seats, a premium sound system, and advanced safety technologies such as lane departure warning and automatic emergency braking. Optional extras included a power sunroof, a navigation system, and a bed liner.
Chassis & Braking
The Silverado 3500 HD features a fully boxed frame constructed from high-strength steel, providing a solid foundation for heavy-duty use. The front suspension utilizes an independent torsion bar setup with double wishbones, while the rear suspension employs a traditional leaf spring design. Braking duties are handled by ventilated disc brakes on all four wheels, with larger rotors and calipers compared to lighter-duty Silverado models. Anti-lock brakes (ABS) are standard, along with electronic stability control. The rear axle ratio varied depending on the specific configuration, influencing both towing capacity and fuel economy.
Market Reception & Comparison
The Duramax/Allison combination in the Silverado 3500 HD was widely praised by automotive critics for its exceptional towing capability and refined driving experience. It consistently outperformed competitors like the Ford Super Duty and Ram Heavy Duty in independent towing tests. While the diesel engine carried a higher price tag than the gasoline options, the increased torque and fuel efficiency made it a worthwhile investment for frequent haulers. Compared to the 6.0L gasoline V8, the Duramax offered significantly better fuel economy when towing, and a much higher maximum towing capacity. Reliability was generally good, although diesel engines require more diligent maintenance than gasoline engines.
Legacy
The 2020-2023 Chevrolet Silverado 3500 HD with the 6.6L Duramax and Allison 10-speed transmission has established itself as a highly capable and reliable heavy-duty truck. The L5P Duramax engine is known for its durability, and the Allison transmission is widely regarded as one of the best in the industry. On the used car market, these trucks command a premium price due to their proven performance and longevity. Properly maintained examples are expected to provide many years of dependable service, making them a popular choice for both commercial and personal use.
