The GMC Sierra 2500HD IV (GMTK2XX) Double Cab Standard 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, represents a significant iteration in GMC’s heavy-duty truck lineage. Produced from 2017 to 2019, this configuration occupied a premium position within the Sierra 2500HD lineup, targeting buyers needing substantial towing and hauling capacity without sacrificing everyday usability. It built upon the foundation of the GMTK2XX platform, known for its robust construction and enhanced capabilities compared to previous generations.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD IV (GMTK2XX) Double Cab Standard 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 | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.5 kg/Hp, 134.2 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 372 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 | 3317 kg (7312.73 lbs.) |
| Max. weight | 4536 kg (10000.17 lbs.) |
| Max load | 1219 kg (2687.43 lbs.) |
| Trunk (boot) space – maximum | 1728 l (61.02 cu. ft.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 5897 kg (13000.66 lbs.) |
| Length | 5842 mm (230 in.) |
| Width including mirrors | 2045 mm (80.51 in.) |
| Height | 1983 mm (78.07 in.) |
| Wheelbase | 3662 mm (144.17 in.) |
| Front track | 1748 mm (68.82 in.) |
| Rear (Back) track | 1709 mm (67.28 in.) |
| Ride height (ground clearance) | 216 mm (8.5 in.) |
| Minimum turning circle (turning diameter) | 15 m (49.21 ft.) |
| Drivetrain Architecture | All wheel drive (4×4). Internal Combustion engine. |
| 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 |
Powertrain & Engine Architecture
The heart of this Sierra 2500HD is the Duramax L5P 6.6-liter turbocharged diesel V8. This engine represents a significant evolution of the Duramax design, incorporating technologies to improve both power and efficiency. The L5P utilizes a cast iron block and aluminum cylinder heads, a robust combination designed for longevity and high cylinder pressures. The engine employs a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. A variable geometry turbocharger (VGT) and intercooler further enhance performance by providing increased air intake and cooling. The overhead valve (OHV) valvetrain, while a more traditional design, is known for its durability and simplicity. The Allison 1000 Series 6-speed automatic transmission is specifically engineered to handle the high torque output of the Duramax engine. This transmission features a lock-up torque converter for improved fuel economy and a heavy-duty cooling system to prevent overheating under demanding conditions.
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 designed for outright speed, this configuration excels in towing and hauling. Acceleration is brisk, even with a substantial load. The Allison transmission shifts smoothly and decisively, providing ample power across the entire rev range. Compared to the gasoline-powered 6.0L V8 option, the Duramax offers significantly more torque at lower RPMs, making it ideal for demanding tasks. The automatic transmission, while convenient, does result in a slight reduction in fuel economy compared to the available manual transmission. However, the convenience and ease of use often outweigh this consideration for many drivers. The 4WD system provides excellent traction in various conditions, enhancing both on-road and off-road capability.
Equipment & Trim Levels
The Double Cab Standard Box configuration typically came well-equipped, positioning it as a mid-to-upper trim level. Standard features generally included air conditioning, power windows and locks, a basic infotainment system with a touchscreen display, and cloth upholstery. Higher trim levels, such as the Denali, added premium features like leather upholstery, heated and ventilated seats, a premium sound system, and advanced safety technologies. Optional extras included a navigation system, a rear-seat entertainment system, and various towing packages. The Double Cab configuration offered a comfortable and spacious cabin for passengers, while the Standard Box provided a practical cargo bed length for a variety of hauling needs.
Chassis & Braking
The GMTK2XX platform 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 leaf springs. This configuration balances ride comfort with load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) is standard. The rear axle ratios varied depending on the specific configuration, influencing both towing capacity and fuel economy. The standard tire sizes ranged from 17 to 20 inches, depending on the trim level.
Market Reception & Comparison
The 6.6-liter Duramax diesel engine consistently received positive reviews for its power, reliability, and fuel efficiency. Critics praised the Sierra 2500HD’s overall capability and comfortable ride. Compared to the gasoline-powered options, the Duramax diesel commanded a higher price but offered significantly lower operating costs, particularly for those who frequently tow or haul heavy loads. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD was often seen as a well-rounded option, offering a good balance of performance, comfort, and features. Fuel economy, while respectable for a heavy-duty truck, was still relatively low compared to smaller vehicles.
Legacy
The Duramax L5P engine has proven to be exceptionally durable and reliable, with many examples exceeding 200,000 miles with proper maintenance. The GMTK2XX platform is also known for its longevity. On the used car market, these Sierra 2500HDs hold their value well, particularly those in good condition with well-documented maintenance records. The combination of a powerful diesel engine, a robust transmission, and a capable chassis makes this a desirable truck for those needing a workhorse that can handle demanding tasks. Regular maintenance, including oil changes, fuel filter replacements, and coolant flushes, is crucial for ensuring the long-term reliability of this powertrain.
