2017-2019 GMC Sierra 3500HD IV (GMTK2XX) Regular Cab Long Box 6.6 Duramax TD V8 (445 Hp) 4WD SRW Automatic

The GMC Sierra 3500HD IV (GMTK2XX) Regular Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower, represents a significant offering in the heavy-duty pickup truck segment. Produced from 2017 to 2019, this configuration was aimed at buyers needing substantial towing and hauling capacity, combining the robust Duramax engine with a capable four-wheel-drive system and a six-speed Allison automatic transmission. This particular variant occupied a premium position within the Sierra 3500HD lineup, catering to those prioritizing power and capability over fuel economy or a more refined ride.

Technical Specifications

INTRODUCTION

The GMC Sierra 3500HD IV, specifically the Regular Cab Long Box configuration with the 6.6L Duramax engine, debuted in 2017 as part of the fourth generation (GMTK2XX) of GMC’s heavy-duty truck line. This generation represented a significant overhaul, focusing on increased capability, improved interior refinement, and enhanced technology. The Regular Cab configuration, paired with the long bed, catered to customers who prioritized cargo space and towing capacity over passenger comfort. The 6.6L Duramax diesel engine was the top-tier engine option, positioning this variant as a workhorse for demanding tasks. It was designed to compete directly with Ford’s Super Duty and Ram’s heavy-duty offerings, appealing to commercial users, ranchers, and those needing a powerful truck for recreational purposes.

Powertrain & Engine Architecture

The heart of this Sierra 3500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine is a testament to modern diesel technology, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly. The L5P utilizes a Bosch common rail fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The engine boasts a variable geometry turbocharger (VGT) and an intercooler to maximize power and efficiency. The overhead valve (OHV) valvetrain, while seemingly traditional, is engineered for durability and low-end torque. The engine’s 16:1 compression ratio contributes to its efficiency and power output. Paired with the engine is the Allison 1000 six-speed automatic transmission, renowned for its durability and ability to handle high torque loads. This transmission features electronically controlled shifts and a lock-up torque converter for improved fuel economy.

Driving Characteristics

The 445 horsepower and 910 lb-ft of torque delivered by the Duramax engine and Allison transmission combination provide impressive performance. While not a sports truck, the Sierra 3500HD offers strong acceleration, even when heavily loaded. The Allison transmission is well-tuned, providing smooth and decisive shifts. The gear ratios are optimized for towing, with lower gears providing ample pulling power. Compared to the gasoline engine options, the Duramax offers significantly more torque at lower RPMs, making it ideal for hauling heavy loads or navigating challenging terrain. Compared to the 6.6L Duramax in earlier generations, the L5P offered a noticeable increase in both horsepower and torque. The Regular Cab configuration, being lighter than crew cab models, contributes to slightly improved acceleration and handling.

Equipment & Trim Levels

The Sierra 3500HD in this configuration typically came standard with features like air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, and a rearview camera. The interior upholstery was typically vinyl or cloth, reflecting the truck’s work-oriented nature. Optional extras included leather upholstery, heated and ventilated front seats, a premium audio system, navigation, and advanced safety features like lane departure warning and forward collision alert. Trim levels varied, but this engine/transmission combo was often found in the SLE or Denali trims, offering a balance of features and capability. The long box provided ample cargo space, making it suitable for a wide range of hauling needs.

Chassis & Braking

The Sierra 3500HD features a fully boxed frame, providing a solid foundation for heavy-duty use. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. This configuration is designed to maximize load-carrying capacity and durability. Braking duties are handled by ventilated disc brakes on all four wheels, with larger rotors at the rear (360mm) compared to the front (355mm). An Anti-lock Braking System (ABS) is standard. The steering system utilizes a cone worm with recirculation balls, providing a robust and reliable steering feel.

Market Reception & Comparison

The 2017-2019 GMC Sierra 3500HD with the Duramax engine 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 heavy-duty truck. Compared to the gasoline engine options, the Duramax offered superior torque and fuel efficiency when towing. Compared to the 6.6L Duramax in previous generations, the L5P was lauded for its increased power and refinement. However, some critics noted the truck’s relatively stiff ride and the higher price tag associated with the Duramax engine.

Legacy

The Duramax L5P engine has proven to be a reliable and durable powerplant. While some early models experienced issues with the fuel injection system, these were largely addressed through software updates and revised components. Today, well-maintained examples of the 2017-2019 Sierra 3500HD with the Duramax engine command a premium in the used car market. The combination of power, capability, and relative reliability makes it a desirable choice for buyers seeking a heavy-duty truck. The Allison transmission continues to be highly regarded for its durability and performance, ensuring that these trucks remain capable workhorses for years to come.