The GMC Sierra 3500HD, specifically the fifth generation (GMTT1XX) produced from 2020 to 2023, represents GMC’s heavy-duty full-size pickup truck offering. This variant, featuring a Regular Cab and Long Bed configuration paired with the 6.6-liter Duramax Turbo Diesel V8 engine producing 445 horsepower, and a ten-speed Allison automatic transmission, was positioned as a work-focused, high-capability truck aimed at customers needing substantial towing and hauling capacity. The “DRW” designation indicates a Dual Rear Wheel configuration, further enhancing its capabilities. This model year marked a significant redesign for the Sierra HD line, incorporating updated styling, technology, and improved functionality.
Technical Specifications
| Brand | GMC |
| Model | Sierra 3500HD |
| Generation | Sierra 3500HD V (GMTT1XX) Regular Cab Long Bed |
| Type (Engine) | 6.6 Duramax TD V8 (445 Hp) DRW Automatic |
| Start of production | 2020 |
| End of production | 2023 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 2 |
| Doors | 2 |
| Fuel Type | Diesel |
| Weight-to-power ratio | 7.6 kg/Hp, 131.9 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 365.7 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 capacity | 29.1 l (30.75 US qt | 25.6 UK qt) |
| Kerb Weight | 3374 kg (7438.4 lbs.) |
| Max. weight | 6350 kg (13999.35 lbs.) |
| Max load | 2976 kg (6560.96 lbs.) |
| Fuel tank capacity | 106 l (28 US gal | 23.32 UK gal) |
| Permitted trailer load with brakes (12%) | 9072 kg (20000.34 lbs.) |
| Length | 5982 mm (235.51 in.) |
| Width including mirrors | 2457 mm (96.73 in.) |
| Height | 2038 mm (80.24 in.) |
| Wheelbase | 3595 mm (141.54 in.) |
| Front track | 1731 mm (68.15 in.) |
| Rear (Back) track | 1905 mm (75 in.) |
| Ride height (ground clearance) | 266 mm (10.47 in.) |
| Drivetrain Architecture | Rear wheel drive. Internal Combustion engine. |
| Number of gears and type of gearbox | 10 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, 355×40 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric 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 |
INTRODUCTION
The 2020-2023 GMC Sierra 3500HD Regular Cab Long Bed with the 6.6L Duramax diesel and Allison automatic transmission represents a significant offering in the heavy-duty truck segment. Built on the GMTT1XX platform, this configuration was designed for buyers prioritizing maximum capability and durability over luxury or passenger space. The Regular Cab configuration, combined with the long bed, provides a practical layout for commercial use or those frequently hauling large loads. This generation Sierra HD aimed to bridge the gap between work-truck functionality and the more refined features expected by modern truck buyers.
Powertrain & Engine Architecture
At the heart of this Sierra 3500HD lies the Duramax L5P 6.6-liter turbocharged diesel V8 engine. This engine is a cornerstone of GMC’s heavy-duty lineup, known for its robust construction and impressive torque output. The L5P utilizes a cast iron block, aluminum cylinder heads, and a variable geometry turbocharger to deliver 445 horsepower at 2800 rpm and a massive 910 lb-ft of torque at 1600 rpm. The engine employs a high-pressure common rail direct fuel injection system, contributing to its efficiency and power delivery. The overhead valve (OHV) valvetrain, while a more traditional design, is favored for its durability and simplicity. Paired with the engine is the Allison 10-speed automatic transmission, a heavy-duty unit specifically designed to handle the engine’s substantial torque. This transmission features electronically controlled shifts and a lock-up torque converter for improved fuel economy and responsiveness.
Driving Characteristics
The combination of the Duramax diesel and the Allison 10-speed automatic results in a driving experience focused on effortless towing and hauling. While not a performance-oriented truck, the 3500HD delivers ample power for accelerating with or without a load. The ten-speed transmission allows the engine to operate within its optimal power band more frequently, providing strong acceleration and minimizing the need for downshifts. Compared to gasoline-powered Sierra 3500HD models, the diesel offers significantly more low-end torque, making it ideal for pulling heavy trailers or navigating challenging terrain. Compared to manual transmission equipped Duramax models, the Allison automatic prioritizes ease of use and convenience, though some drivers may prefer the greater control offered by a manual gearbox. The DRW configuration enhances stability when towing, distributing the weight more evenly across the rear axle.
Equipment & Trim Levels
The Regular Cab Long Bed 3500HD typically came with a functional, work-oriented interior. Standard features included a basic infotainment system with a touchscreen display, air conditioning, and vinyl upholstery. Higher trim levels, such as the SLE or Denali, added features like leather upholstery, heated seats, a premium sound system, and advanced safety technologies. Optional extras included a trailer brake controller, a gooseneck hitch, and various bed accessories. The interior design prioritized durability and ease of cleaning, reflecting the truck’s intended use. The dashboard layout was straightforward and functional, with clearly labeled controls.
Chassis & Braking
The Sierra 3500HD’s chassis is built for heavy-duty use. It features a fully boxed frame constructed from high-strength steel. The front suspension utilizes coil springs and a double wishbone design, while the rear suspension employs a traditional leaf spring setup. The DRW configuration utilizes a wider rear axle to improve stability and load-carrying capacity. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power even when heavily loaded. An Anti-lock Braking System (ABS) is standard. The steering system is a rack-and-pinion setup with electric power steering, offering responsive handling and reduced driver fatigue.
Market Reception & Comparison
The 2020-2023 GMC Sierra 3500HD with the Duramax diesel and Allison automatic received generally positive reviews. Critics praised its impressive towing and hauling capabilities, comfortable ride quality (for a heavy-duty truck), and refined interior. Compared to its competitors, such as the Ford Super Duty and Ram 3500, the Sierra 3500HD offered a compelling combination of power, technology, and refinement. Fuel economy, while improved with the 10-speed transmission, remained relatively low compared to lighter-duty trucks. Reliability has been generally good, although some owners have reported issues with the diesel emissions system.
Legacy
The Duramax L5P engine and Allison 10-speed automatic transmission have proven to be a durable and reliable powertrain combination. These trucks continue to hold their value well in the used car market, particularly those in good condition with well-documented maintenance histories. The 2020-2023 Sierra 3500HD represents a significant step forward in heavy-duty truck technology, offering a compelling blend of capability, comfort, and refinement. The DRW configuration remains a popular choice for those requiring maximum towing capacity, and the L5P Duramax engine is widely regarded as one of the best diesel engines available in a heavy-duty pickup truck.
