The GMC Sierra 2500HD IV (GMTK2XX) Regular Cab Long Box, equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower and paired with a 6-speed Allison automatic transmission and four-wheel drive, was a key offering in GMC’s heavy-duty pickup truck lineup from 2017 to 2019. This configuration represented a robust, work-oriented variant within the fourth generation of the Sierra 2500HD, designed for demanding tasks like towing and hauling. It occupied a position between the less powerful gasoline engine options and the even more capable, but also more expensive, trims focused on maximum towing capacity.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD IV (GMTK2XX) Regular Cab Long Box |
| Type (Engine) | 6.6 Duramax TD V8 (445 Hp) 4WD Automatic |
| Start of production | 2017 |
| End of production | 2019 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 2 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 6.2 kg/Hp, 161.8 Hp/tonne |
| Weight-to-torque ratio | 2.2 kg/Nm, 448.6 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 | 29.7 l (31.38 US qt | 26.13 UK qt) |
| Kerb Weight | 2751 kg (6064.92 lbs.) |
| Max. weight | 4309 kg (9499.72 lbs.) |
| Max load | 1558 kg (3434.8 lbs.) |
| Trunk (boot) space – maximum | 2160 l (76.28 cu. ft.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 6577 kg (14499.8 lbs.) |
| Length | 5699 mm (224.37 in.) |
| Width including mirrors | 2035 mm (80.12 in.) |
| Height | 1975 mm (77.76 in.) |
| Wheelbase | 3393 mm (133.58 in.) |
| Minimum turning circle (turning diameter) | 14 m (45.93 ft.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front wheels engaged via clutch. |
| Number of gears and type of gearbox | 6 gears, automatic transmission Allison |
| Front suspension | Coil spring, Double wishbone, Transverse stabilizer |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 350×40 mm |
| Rear brakes | Ventilated discs, 360×34 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Tires size | 235/80 R17; 265/70 R17; 265/70 R18; 265/60 R20 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 20 |
INTRODUCTION
The 2017-2019 GMC Sierra 2500HD Regular Cab Long Box with the 6.6L Duramax diesel and Allison automatic transmission was a workhorse pickup truck designed for serious towing and hauling. Built on the GMTK2XX platform, this generation of Sierra HD trucks represented a significant step forward in capability and refinement compared to its predecessors. The Regular Cab configuration, combined with the long bed, catered to buyers prioritizing practicality and cargo space over passenger comfort. This particular variant, with its potent diesel engine and robust transmission, was aimed at professionals and individuals needing a dependable truck for demanding applications.
Powertrain & Engine Architecture
At the heart of this Sierra 2500HD lies the Duramax L5P 6.6-liter turbocharged diesel V8 engine. 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 common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The turbocharger, coupled with an intercooler, provides increased air intake, boosting power and torque. The engine’s overhead valve (OHV) valvetrain, while seemingly traditional, is known for its durability and reliability. The Allison 1000 Series 6-speed automatic transmission is specifically designed to handle the immense torque output of the Duramax engine. This transmission features a lock-up torque converter for improved fuel efficiency and a heavy-duty cooling system to prevent overheating under strenuous conditions. The transmission’s gear ratios are optimized for both towing and everyday driving, providing a balance of power and efficiency.
Driving Characteristics
The 445 horsepower and 910 lb-ft of torque delivered by the Duramax engine and Allison transmission combination translate into impressive real-world performance. While not a sports truck, the Sierra 2500HD offers strong acceleration, even when heavily loaded. The Allison transmission shifts smoothly and decisively, providing ample power for merging onto highways and climbing steep grades. Compared to the gasoline engine options, the diesel provides significantly more low-end torque, making it ideal for towing heavy trailers. Compared to higher-output Duramax variants, this 445 hp version offers a slightly more manageable power delivery, making it easier to control for drivers less experienced with heavy-duty trucks. The 6-speed automatic, while capable, doesn’t offer the same level of gear ratios as some newer transmissions, but it remains a reliable and durable unit.
Equipment & Trim Levels
The Sierra 2500HD Regular Cab Long Box in this configuration typically came standard with features geared towards work and utility. This included a basic audio system, vinyl upholstery, air conditioning, and power windows and locks. The interior was functional and durable, prioritizing practicality over luxury. Optional extras included upgraded audio systems, a navigation system, leather upholstery, heated seats, and various towing packages. The exterior typically featured black bumpers and grille surrounds, reflecting its work-oriented nature. Chrome accents were available as options, adding a touch of visual appeal.
Chassis & Braking
The Sierra 2500HD’s chassis is built for heavy-duty use. It features a fully boxed frame constructed from high-strength steel, providing a solid foundation for towing and hauling. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. This configuration provides a comfortable ride, even when the truck is loaded. 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. The rear axle ratios varied depending on the specific configuration, influencing both towing capacity and fuel economy.
Market Reception & Comparison
The 2017-2019 GMC Sierra 2500HD with the 6.6L Duramax and Allison automatic received generally positive reviews. Critics praised its powerful engine, robust transmission, and impressive towing capacity. Fuel economy, while not exceptional, was considered reasonable for a heavy-duty diesel truck. Compared to the gasoline engine options, the Duramax diesel offered significantly better fuel economy when towing heavy loads. Compared to the Ford Super Duty and Ram 2500/3500, the Sierra 2500HD was often seen as a balanced offering, providing a good combination of capability, comfort, and value. Some reviewers noted that the interior, while functional, lacked the refinement of some competitors.
Legacy
The Duramax L5P engine and Allison 1000 Series transmission have proven to be exceptionally reliable powertrains. Well-maintained examples of the 2017-2019 Sierra 2500HD continue to command strong resale values in the used car market. The combination of durability, capability, and relatively low maintenance costs makes this truck a popular choice for buyers seeking a dependable workhorse. While newer heavy-duty trucks offer more advanced technology and features, the GMTK2XX Sierra 2500HD remains a capable and practical option for those needing a robust pickup truck for demanding tasks. Common issues reported with these trucks are typically related to emissions control systems, such as the diesel particulate filter, but the core powertrain remains remarkably robust.
