DFC Diesel TH590304STAUSOALBHD Tow/Haul HD Series Speed of Air Long Block Crate Engine (STD/Auto) | 2003-2004 Dodge RAM 5.9L Cummins

Features:

• Built to support up to 900 horsepower
• Includes Fluidamper for smoother operation
• Wagler connecting rods for extreme strength
• Balanced rotating assembly enhances durability
• Heavy-duty flexplate handles high torque loads
• Includes all Tow/Haul and Street upgrades
• Backed by 5-year, 160,000 km warranty
• Designed for street use and heavy towing
• Compatible with standard and automatic transmissions
• Ceramic-coated pistons resist extreme heat
• Advanced CNC machining ensures precise fit
• HD performance with street-drive reliability

Get Real Power Without Losing Street Manners

When you need serious horsepower without giving up street reliability, the DFC Tow/Haul HD Series Long Block is built to do both. This engine is designed for 2003-2004 Dodge 5.9L Cummins owners who want to tow heavy, drive daily, and still have room to push well into high-performance territory. It’s capable of supporting up to 900 horsepower with the right setup, but more importantly, it’s been balanced for real-world use between 650 and 800 horsepower. That means it can handle weekend hauls, trailer towing, and even long road trips without skipping a beat. The HD flexplate and Fluidamper help smooth out vibrations and reinforce the rotating assembly so you get strength and comfort all in one package. Wagler connecting rods and ceramic-coated pistons add strength where it counts, giving you the confidence to turn up the power without stressing over reliability. This is the kind of long block that gives you high performance without the headaches that come with most high-strung builds.

Reinforced From The Inside Out For Heavy Loads

The TH590304STAUSOALBHD long block from DFC’s Tow/Haul HD Series is engineered with upgraded internals for extreme duty performance and durability. It includes all the core enhancements found in the Street and Tow/Haul series models, but adds heavy-duty components like Wagler connecting rods and a fully balanced rotating assembly. A Fluidamper comes standard to reduce torsional vibrations, working alongside the upgraded HD flexplate to better handle high torque output under load. The pistons feature ceramic-coated crowns and dry film skirts for better heat resistance and reduced friction, especially during prolonged towing or hauling. This engine also comes with preset valvetrain geometry, a CNC-machined block, and a fully remanufactured head complete with all new valves, guides, and seals. While it's designed to support up to 900 horsepower at the flywheel, its real-world sweet spot is for trucks operating between 650 and 800 horsepower. It’s a serious build for owners who demand more power and endurance than a stock setup can offer.

Fits:  2003, 2004 Dodge RAM 5.9L Cummins

Notes:

• Core return is likely required after purchase
• Built for 2003-2004 5.9L Cummins applications
• Supports up to 900 HP with correct setup
• Ideal power range is between 650 and 800 HP
• Rated HP is measured at the engine flywheel
• Compatible with automatic and standard transmissions
• Includes all Street and Tow/Haul Series upgrades
• Considered a severe duty engine application
• Requires more frequent service intervals per warranty
• 5-year, 160,000 km warranty still applies
• Professional installation is strongly recommended

Street Series vs Tow/Haul vs Tow/Haul HD

• Street Series: Ideal for daily driving, light work, and diesel enthusiasts. Focuses on reliability upgrades over stock, with head stud and sealing improvements.

• Tow/Haul Series: All Street upgrades plus added performance parts for higher load and towing power. Supports builds up to ~700 HP.

• Tow/Haul HD Series: The most robust option. Adds heavy-duty internals like Wagler rods and a balanced rotating assembly for 800+ HP capability.

Standard/Auto vs Standard vs Auto

• Standard/Auto: Compatible with both manual and automatic transmissions. Offers the most flexibility.

• Standard: Built specifically for manual transmission configurations.

• Auto: Built specifically for automatic transmission setups.