2017-2019 GMC Sierra 2500HD IV (GMTK2XX) Regular Cab Long Box 6.6 Duramax TD V8 (445 Hp) Automatic

Technical Specifications

The fourth-generation GMC Sierra 2500HD (GMTK2XX platform) represented a significant leap forward in heavy-duty truck design and capability. Introduced for the 2017 model year, it featured a fully redesigned chassis, body, and interior. The Regular Cab Long Box configuration, paired with the 6.6L Duramax diesel and Allison automatic, was specifically tailored for customers prioritizing maximum payload and towing capacity in a no-frills package. This truck was primarily sold in North America, catering to the demands of agricultural workers, construction crews, and those needing a robust vehicle for demanding tasks.

Powertrain & Engine Architecture

The heart of this Sierra 2500HD 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 produces 445 horsepower at 2800 rpm and a massive 910 lb-ft (1234 Nm) of torque at 1600 rpm. The overhead valve (OHV) valvetrain, while seemingly traditional, is known for its durability and simplicity. The Allison 1000 Series 6-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. This transmission features electronically controlled shifts and a lock-up torque converter for improved fuel efficiency. The transmission’s gear ratios are optimized for both towing and hauling, providing strong acceleration and confident power delivery even under heavy loads.

Driving Characteristics

The 6.6L Duramax/Allison combination in the Sierra 2500HD delivers a driving experience that is both powerful and surprisingly refined. While not as quick as gasoline-powered counterparts, the sheer torque output allows for effortless towing and hauling. The Allison transmission shifts smoothly and decisively, providing a seamless power delivery. Compared to the 6.0L gasoline V8 option, the Duramax offers significantly more low-end torque, making it ideal for challenging terrain and heavy loads. Compared to higher-output Duramax variants found in the 3500HD, this 445hp version offers a slightly more manageable power curve, making it easier to control when towing at maximum capacity. The long box configuration contributes to a comfortable ride, absorbing bumps and providing a stable platform for hauling. However, the truck’s size and weight are noticeable in tight maneuvering situations.

Equipment & Trim Levels

The Regular Cab Long Box 2500HD typically came with a relatively basic level of standard equipment, focusing on functionality and durability. Standard features included air conditioning, a basic audio system, vinyl upholstery, and manual windows and locks. However, options were available to enhance comfort and convenience. These included power windows and locks, a premium audio system, upgraded cloth or leather upholstery, and a rearview camera. The work truck (WT) trim was the most common for this configuration, prioritizing affordability and practicality. SLT trim added some additional comfort and convenience features.

Chassis & Braking

The GMTK2XX chassis is a fully boxed frame designed for maximum strength and rigidity. The front suspension utilizes coil springs and a double wishbone design with a transverse stabilizer bar, providing a comfortable ride and stable handling. The rear suspension employs a traditional leaf spring setup, optimized for heavy-duty hauling. Braking duties are handled by ventilated disc brakes at all four corners, providing ample stopping power even when towing. An Anti-lock Braking System (ABS) is standard. The rear axle ratios varied depending on the specific configuration, but were generally geared for towing and hauling, prioritizing torque over fuel economy.

Market Reception & Comparison

The GMC Sierra 2500HD with the Duramax diesel and Allison automatic received generally positive reviews from automotive critics. It was praised for its powerful engine, smooth transmission, and impressive towing capacity. Fuel economy, while not a primary concern for heavy-duty truck buyers, was considered acceptable for a vehicle of its size and capability. Compared to the Ford Super Duty and Ram 2500, the Sierra 2500HD was often seen as offering a good balance of power, refinement, and value. The Duramax engine was consistently ranked among the best diesel engines in the heavy-duty truck segment. Reliability was generally good, although diesel engines can be more expensive to maintain than gasoline engines due to the complexity of the fuel injection system and emissions controls.

Legacy

The 6.6L Duramax L5P engine and Allison 1000 transmission have proven to be exceptionally durable and reliable powertrains. Used examples of the 2017-2019 Sierra 2500HD continue to command strong resale values, particularly those that have been well-maintained. The L5P Duramax is known for its longevity and ability to withstand high mileage. While diesel emissions systems can require occasional maintenance, the core engine and transmission components are generally robust. This particular configuration remains a popular choice for buyers seeking a capable and dependable heavy-duty truck for work or recreational purposes.