The GMC Sierra 2500HD, in its fifth generation (GMTT1XX), received a significant refresh for the 2024 model year. This article focuses specifically on the Regular Cab Long Bed configuration equipped with the 6.6-liter Duramax Turbo Diesel V8 engine producing 470 horsepower, paired with a 10-speed Allison automatic transmission. Introduced in 2023 with the facelift, this variant represents a work-focused iteration of the Sierra 2500HD lineup, prioritizing towing capacity and durability over luxury appointments. It occupies a position as a robust, high-output option for buyers needing serious capability, slotting above the gasoline-powered engines and below the more luxurious Denali trims.
Technical Specifications
| Brand | GMC |
| Model | Sierra 2500HD |
| Generation | Sierra 2500HD V (GMTT1XX, facelift 2024) Regular Cab Long Bed |
| Type (Engine) | 6.6 Duramax TD V8 (470 Hp) Automatic |
| Start of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 2 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 6.6 kg/Hp, 151.9 Hp/tonne |
| Weight-to-torque ratio | 2.3 kg/Nm, 427.1 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 | 28.5 l (30.12 US qt | 25.08 UK qt) |
| Kerb Weight | 3095 kg (6823.31 lbs.) |
| Max. weight | 4785 kg (10549.12 lbs.) |
| Max load | 1690 kg (3725.81 lbs.) |
| Fuel tank capacity | 106 l (28 US gal | 23.32 UK gal) |
| Permitted trailer load with brakes (12%) | 6577 kg (14499.8 lbs.) |
| Length | 6002 mm (236.3 in.) |
| Width including mirrors | 2076 mm (81.73 in.) |
| Height | 2030 mm (79.92 in.) |
| Wheelbase | 3595 mm (141.54 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 259 mm (10.2 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine (ICE) drives the rear wheels. |
| Drive wheel | Rear wheel drive |
| 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 Steering |
| 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 is the 6.6-liter L5P Duramax turbo-diesel V8. This engine, a staple in GMC and Chevrolet heavy-duty trucks for years, utilizes a cast iron block and aluminum cylinder heads. The L5P features a common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. A variable geometry turbocharger (VGT) and intercooler work in tandem to maximize power and efficiency. The engine employs an overhead valve (OHV) valvetrain, a design choice prioritizing durability and low-end torque over high-revving performance. The 10-speed Allison automatic transmission, introduced with the GMTT1XX generation, is a robust unit designed to handle the engine’s substantial torque output. It features electronically controlled shifts and a wide gear ratio spread, optimizing both towing performance and fuel economy.
Driving Characteristics
The 470 horsepower and 1322 lb-ft of torque delivered by this powertrain combination translate into impressive real-world performance. While not designed for rapid acceleration, the Sierra 2500HD excels at hauling heavy loads. The 10-speed Allison transmission keeps the engine in its optimal power band, providing smooth and confident acceleration even when towing near its maximum capacity. Compared to the gasoline-powered 6.6L V8, the Duramax offers significantly more low-end torque, making it easier to start and maintain momentum with heavy trailers. The automatic transmission, while convenient, may not offer the same level of control as a manual transmission for precise engine braking on steep descents. The gear ratios are tuned for work, prioritizing pulling power over fuel efficiency at highway speeds.
Equipment & Trim Levels
The Regular Cab Long Bed 2500HD with the Duramax engine typically came with a relatively basic level of standard equipment, reflecting its work-truck focus. Standard features generally included air conditioning, a basic infotainment system with a touchscreen display, and vinyl upholstery. However, options were available to enhance comfort and convenience. These included upgraded infotainment systems with navigation, leather upholstery, power-adjustable seats, and a premium audio system. The interior design is functional and durable, prioritizing ease of cleaning and long-term reliability.
Chassis & Braking
The Sierra 2500HD’s chassis is built for heavy-duty use. It features a fully boxed frame constructed from high-strength steel. The front suspension utilizes an independent torsion bar setup with double wishbone components, providing a comfortable ride even when unladen. The rear suspension employs a traditional leaf spring design, optimized for load-carrying capacity. Braking duties are handled by ventilated disc brakes at all four corners, providing ample stopping power. An Anti-lock Braking System (ABS) is standard. Due to the truck’s weight and intended use, rear drum brakes were sometimes fitted on lower trim levels, while higher trims received rear discs.
Market Reception & Comparison
The Duramax diesel engine has consistently been praised for its reliability and longevity. Critics generally lauded the 2024 Sierra 2500HD’s towing capacity and overall capability. Compared to the gasoline-powered versions, the Duramax offered superior fuel economy when towing heavy loads, although it came at a higher initial cost. The 10-speed Allison transmission was also well-received for its smooth shifting and wide gear ratio spread. However, some reviewers noted that the interior, while functional, lacked the refinement of some competitors, particularly the Ram 2500HD.
Legacy
The L5P Duramax engine has proven to be exceptionally durable, with many examples exceeding 200,000 miles with proper maintenance. The 10-speed Allison transmission has also demonstrated good reliability. On the used car market, these Sierra 2500HDs hold their value well, particularly those that have been well-maintained and have a documented service history. The combination of a powerful diesel engine, a robust transmission, and a heavy-duty chassis makes this variant a popular choice for buyers seeking a capable and reliable work truck. The GMTT1XX platform, even with the 2024 refresh, continues to be a strong contender in the heavy-duty truck segment, known for its longevity and ability to withstand demanding use.
