DFC Diesel TH6604505LLYSOALBHD Tow/Haul HD Series Speed Of Air Long Block (Standard/Auto) | 2004.5-2005 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LLY

Features:

• Rated for up to 900HP at the flywheel
• Built for towing between 500 and 750HP
• Includes Callies Compstar forged crankshaft
• Wagler forged connecting rods increase strength
• Wagler Stage 1 alternate firing camshaft included
• Balanced rotating assembly improves engine smoothness
• Heavy-duty flexplate handles added torque
• ATI dampener reduces engine harmonics
• Includes all Street and Tow/Haul upgrades
• Fully remanufactured to exceed OEM specifications
• Backed by 5-year, 160,000 km warranty
• Ideal for high-power towing and street driving

Take Your Duramax Build To Extreme Street Power

If you're looking to push your 2004.5-2005 Duramax LLY beyond stock limits while still keeping it streetable and ready to tow, the DFC Tow/Haul HD Series Long Block is built to get the job done, and then some. This is DFC’s most capable LLY engine for serious enthusiasts who demand both performance and durability. Whether you’re hauling heavy loads on the highway or laying down big power on the dyno, this engine is engineered to deliver consistent strength under pressure. It's designed to support up to 900HP at the flywheel, with a sweet spot between 500 and 750HP for towing and everyday driving. Reinforced with premium internals like Wagler forged rods, a Callies Compstar crankshaft, and a balanced rotating assembly, this long block is anything but ordinary. You’ll also get a Wager alternate firing camshaft, HD flexplate, and ATI damper, all working together to reduce stress and maximize longevity. It’s a true power-ready foundation that doesn't sacrifice drivability, and it's backed by DFC’s industry-leading 5-year, 160,000 km warranty for total confidence on and off the road.

Reinforced From The Crank Up For Maximum Output

The DFC TH6604505LLYSOALBHD Tow/Haul HD Series Long Block is a precision-built engine tailored for 2004.5-2005 GM and Chevrolet 2500HD and 3500HD trucks running the 6.6L Duramax LLY. Designed for drivers who need serious power without giving up reliability, this build includes all the upgrades from the Street and Tow/Haul Series, with added hardware for high-performance towing and street use. At the heart of it is a Callies Compstar crankshaft and a fully balanced rotating assembly, offering smoother operation and improved high-RPM stability. Wagler forged connecting rods provide the bottom-end strength needed to handle up to 900HP, while the Wager Stage 1 alternate firing camshaft helps reduce harmonics and improve cylinder balance under load. Supporting components like the HD flexplate and ATI dampener are included to handle the torque and vibration that come with big power. The engine block is bored for oversize pistons and machined to tight tolerances using Rottler equipment, while the heads are fully remanufactured with all-new internals. This long block is designed for those who tow hard, drive aggressively, and need a build that won’t flinch under pressure.

Fits: 2004.5, 2005 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LLY

Notes:

• Designed for 2004.5-2005 GM/Chevy 2500HD and 3500HD trucks with the 6.6L Duramax LLY engine
• Tow/Haul HD Series is ideal for high-power towing and street performance builds
• Rated for up to 900HP at the flywheel, with optimal performance between 500 and 750HP for towing applications
• Includes all upgrades from the Street Series and Tow/Haul Series for enhanced strength and reliability
• Forged Wagler connecting rods improve bottom-end durability under heavy load
• Callies Compstar crankshaft and balanced rotating assembly provide smoother high-power operation
• Wager Stage 1 alternate firing camshaft reduces internal engine harmonics
• Includes heavy-duty flexplate and ATI dampener for added torque handling and vibration control
• Engine is fully remanufactured using all new or OEM-equivalent internal components
• Block is machined and bored to accept next oversize pistons
• Comes with DFC’s 5-year or 160,000 km (100,000 mile) limited warranty
• Professional installation is highly recommended due to the engine’s performance capabilities

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.