The GMC Sierra 3500HD, 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 designed for demanding tasks like towing and hauling. The Double Cab Long Bed configuration, paired with the 6.6-liter Duramax Turbo-Diesel V8 engine producing 470 horsepower and equipped with a 10-speed Allison automatic transmission and four-wheel drive, represents a premium and capable trim level within the 3500HD lineup. Introduced in 2024, this variant caters to buyers needing substantial capability without sacrificing comfort or technology.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX, facelift 2024) Double Cab Long Bed |
| Type (Engine) | 6.6 Duramax TD V8 (470 Hp) 4WD SRW Automatic |
| Start of production | 2024 |
| 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 | 28.5 l (30.12 US qt | 25.08 UK qt) |
| Kerb Weight | 3468 kg (7645.63 lbs.) |
| Max. weight | 5511 kg (12149.68 lbs.) |
| Max load | 2043 kg (4504.04 lbs.) |
| Fuel tank capacity | 136 l (35.93 US gal | 29.92 UK gal) |
| Permitted trailer load with brakes (12%) | 9072 kg (20000.34 lbs.) |
| Length | 6534 mm (257.24 in.) |
| Width including mirrors | 2079 mm (81.85 in.) |
| Height | 2054 mm (80.87 in.) |
| Wheelbase | 4127 mm (162.48 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1736 mm (68.35 in.) |
| Ride height (ground clearance) | 284 mm (11.18 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, 355×40 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 | 275/70 R18; 275/65 R20 |
| Wheel rims size | 8J x 18; 8.5J x 20 |
Powertrain & Engine Architecture
The heart of this Sierra 3500HD is the 6.6-liter L5P Duramax turbo-diesel V8 engine. This engine is a cornerstone of GMC’s heavy-duty lineup, known for its robust construction and substantial torque output. The L5P utilizes a cast iron block, aluminum cylinder heads, and a forged steel crankshaft. It employs a diesel commonrail fuel injection system, delivering highly pressurized fuel directly into the cylinders for efficient combustion. The engine features an overhead valve (OHV) valvetrain, a design choice prioritizing durability and low-end torque. A single variable geometry turbocharger with an intercooler further enhances performance. The 10-speed Allison automatic transmission is specifically tuned to handle the engine’s immense torque, 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 translate into exceptional towing and hauling capabilities. The 10-speed Allison transmission is crucial in managing this power, offering a wide range of gear ratios to keep the engine in its optimal power band. While not designed for outright speed, the Sierra 3500HD provides confident acceleration even when heavily loaded. Compared to gasoline-powered versions of the Sierra 3500HD, the Duramax diesel offers significantly more low-end torque, making it ideal for demanding tasks. Compared to earlier Duramax engines, the L5P benefits from improved refinement and reduced noise, vibration, and harshness (NVH). The four-wheel-drive system provides enhanced traction in various conditions, making it suitable for both on-road and off-road use.
Equipment & Trim Levels
The 2024 Sierra 3500HD Double Cab Long Bed with the Duramax engine typically comes standard with a high level of equipment. This includes features like a large infotainment touchscreen with Apple CarPlay and Android Auto compatibility, a premium audio system, and advanced safety technologies such as automatic emergency braking and lane departure warning. Interior upholstery is typically cloth or leather, depending on the specific sub-trim level (e.g., SLE, AT4, Denali). Optional extras include a power sunroof, heated and ventilated front seats, a rear-seat entertainment system, and a head-up display. The Double Cab configuration provides comfortable seating for five passengers, while the Long Bed offers ample cargo space.
Chassis & Braking
The Sierra 3500HD utilizes a fully boxed frame constructed from high-strength steel, providing a solid foundation for heavy-duty applications. The front suspension features an independent torsion bar setup with double wishbone control arms, while the rear suspension employs a traditional leaf spring design. 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 even when towing heavy loads. The front brakes measure 355x40mm, while the rear brakes are 360x34mm. An Anti-lock Braking System (ABS) is standard, enhancing safety and control. The steering system utilizes a hydraulic power steering setup, providing a responsive and predictable feel.
Market Reception & Comparison
The 2024 GMC Sierra 3500HD with the 6.6-liter Duramax engine has been well-received by critics and consumers alike. It is consistently praised for its exceptional towing and hauling capabilities, comfortable ride quality, and refined interior. Compared to other heavy-duty trucks in its class, such as the Ford Super Duty and Ram 3500, the Sierra 3500HD offers a compelling combination of power, refinement, and technology. Fuel economy is typical for a heavy-duty diesel truck, with EPA estimates varying depending on configuration and driving conditions. Reliability has generally been good, although diesel engines can be more complex and potentially more expensive to maintain than gasoline engines.
Legacy
The Duramax diesel engine has established a strong reputation for durability and longevity. The L5P variant, introduced in 2017, continues this legacy with its robust construction and advanced technologies. On the used car market, Sierra 3500HD models equipped with the Duramax engine and Allison transmission hold their value well due to their proven capabilities and reliability. Proper maintenance, including regular oil changes and fuel filter replacements, is crucial for ensuring the long-term health of this powertrain. The 2024 facelift further enhances the Sierra 3500HD’s appeal, solidifying its position as a leading contender in the heavy-duty truck segment.
