The GMC Sierra 2500HD, in its fifth generation (GMTT1XX), received a significant facelift for the 2024 model year. This iteration represents GMC’s heavy-duty full-size pickup truck offering, positioned above the Sierra 1500 and aimed at buyers requiring substantial towing and payload capacity. The Double Cab Long Bed configuration, paired with the 6.6-liter Duramax Turbo-Diesel V8 engine producing 470 horsepower and coupled with a 10-speed Allison automatic transmission, represents a premium offering within the 2500HD lineup, balancing capability with a degree of refinement. Production of this specific configuration began with the 2023 model year and continues through the current generation.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX, facelift 2024) Double Cab Long Bed |
| Type (Engine) | 6.6 Duramax TD V8 (470 Hp) 4WD Automatic |
| Start of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.4 kg/Hp, 135.5 Hp/tonne |
| Weight-to-torque ratio | 2.6 kg/Nm, 381.2 Nm/tonne |
| Power | 470 Hp @ 2800 rpm |
| Power per litre | 71.2 Hp/l |
| Torque | 1322 Nm @ 1600 rpm (975.06 lb.-ft. @ 1600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | 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 capacity | 28.5 l (30.12 US qt | 25.08 UK qt) |
| Kerb Weight | 3468 kg (7645.63 lbs.) |
| Max. weight | 5080 kg (11199.48 lbs.) |
| Max load | 1612 kg (3553.85 lbs.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 7983 kg (17599.5 lbs.) |
| Length | 6534 mm (257.24 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2027 mm (79.8 in.) |
| Wheelbase | 4127 mm (162.48 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 257 mm (10.12 in.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front engaged via clutch. |
| 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, 350×40 mm |
| Rear brakes | Ventilated discs, 360×34 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Power steering | Hydraulic |
| Tires size | 235/80 R17; 265/70 R17; 245/75 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 variant is the 6.6-liter L5P Duramax turbo-diesel V8 engine. This engine represents a significant evolution of GMC’s diesel offerings, featuring a cast iron block, aluminum cylinder heads, and a robust rotating assembly designed for high torque output. The engine utilizes a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. A single variable geometry turbocharger with an intercooler provides increased air intake, contributing to both power and efficiency. The overhead valve (OHV) valvetrain, while a more traditional design, is known for its durability and simplicity. The 10-speed Allison automatic transmission is specifically calibrated for the Duramax engine’s torque characteristics, providing smooth and efficient power delivery. This transmission features electronically controlled shifts and a tow/haul mode optimized for heavy loads.
Driving Characteristics
The 470 horsepower and 1322 lb-ft of torque delivered by this powertrain configuration results in impressive performance, even when heavily loaded. While not designed for outright speed, the Sierra 2500HD offers strong acceleration and effortless towing capability. The 10-speed Allison transmission helps to keep the engine in its optimal power band, providing responsive shifts and minimizing gear hunting. Compared to gasoline-powered versions of the Sierra 2500HD, this diesel variant excels in situations requiring substantial low-end torque, such as hauling heavy trailers or navigating steep grades. The automatic transmission, while convenient, may not offer the same level of driver engagement as a manual transmission, but it simplifies operation for everyday driving and towing scenarios.
Equipment & Trim Levels
The 2500HD Double Cab Long Bed with the Duramax engine typically falls into the mid-to-upper trim levels, such as the SLE or AT4. Standard features generally include a user-friendly infotainment system with touchscreen display, Apple CarPlay and Android Auto compatibility, and a suite of safety features like automatic emergency braking and lane departure warning. Interior upholstery typically consists of cloth or leather, with options for heated and ventilated front seats. Optional extras often include a premium audio system, a power sunroof, and advanced trailering technologies such as trailer sway control and integrated trailer brake controller.
Chassis & Braking
The Sierra 2500HD utilizes a body-on-frame construction, providing a robust platform for heavy-duty applications. The front suspension features an independent torsion bar setup with double wishbones, while the rear suspension employs a traditional leaf spring design. This configuration is optimized for load-carrying capacity and stability. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when towing. The ABS system helps to maintain control during emergency braking situations. The heavy-duty chassis and braking system are designed to handle the increased weight and demands of this powertrain configuration.
Market Reception & Comparison
The Duramax diesel engine has consistently been praised for its reliability, durability, and impressive torque output. Critics generally view the 2500HD with the 6.6-liter Duramax and 10-speed Allison as a top contender in the heavy-duty pickup truck segment. Compared to the gasoline-powered 6.6-liter V8, the diesel offers significantly better fuel economy when towing and hauling. However, the diesel engine typically carries a higher price tag and may require more expensive maintenance. Compared to competitors like the Ford Super Duty and Ram 2500, the Sierra 2500HD offers a compelling combination of capability, comfort, and technology.
Legacy
The L5P Duramax engine has proven to be a remarkably reliable powertrain, with many examples exceeding 200,000 miles with proper maintenance. The 10-speed Allison transmission has also demonstrated good durability. In the used car market, Sierra 2500HD models equipped with this powertrain configuration command a premium due to their reputation for longevity and capability. These trucks remain popular choices for owners who require a robust and dependable workhorse for demanding tasks. The combination of a powerful diesel engine, a smooth-shifting automatic transmission, and a heavy-duty chassis ensures that the 2023+ GMC Sierra 2500HD will continue to be a sought-after vehicle for years to come.
