Big power turbo, supercharged, and nitrous builds put more stress on a torque converter than the factory E4OD unit was ever designed to handle. The Circle D Pro Series E4OD Torque Converter is a fully custom billet converter available in three diameters, giving you the ability to match the converter to your exact power level and driving style rather than settling for a one size fits all upgrade.
252mm: built for maximum power and adjustability. Designed for 800+ horsepower applications, the 252mm is the smallest and most aggressive diameter in the lineup, built for big turbo, blower, or nitrous combinations. A CNC machined steel stator gives Circle D the ability to fine tune this converter's behavior to your specific setup, and a mechanical diode one way clutch improves efficiency compared to the factory roller clutch design. Anti-balloon plates on the pump and turbine keep internal components from flexing under extreme cylinder pressure, and the billet front cover adds strength right where factory covers are known to fail.
258mm: a strong mix of drivability and performance. The 258mm uses a 10 1/4" core built for turbo and positive displacement blower combinations that want quicker spool and improved launch while still maintaining good top end efficiency. It's built with 100 square inches of clutch lining for wide open throttle lock-up, giving it far more holding capacity than the factory single disc setup, while still being a converter you can drive comfortably every day.
265mm: the strongest option for serious power. The 265mm uses a multi disc clutch pack, making it Circle D's most durable option for gas and diesel E4OD trucks running big power. Like the other diameters it features 100 square inches of clutch lining for wide open throttle lock-up, giving it the holding capacity to handle serious torque without slipping or generating excess heat, whether you're running it on the street or at the track.
Shared construction across every diameter. All three Pro Series converters are furnace brazed and hand TIG welded rather than stamped and glued like the factory unit, use Torrington style bearings to reduce friction and extend service life, and feature a flanged impeller hub for anti-flex durability. Every converter is hand assembled to exacting tolerances, which is what separates a true Pro Series build from a standard rebuilt or off the shelf converter.
Product Benefits
- Available in 252mm, 258mm, and 265mm diameters
- 252mm designed for 800+ horsepower
- CNC machined steel stator (252mm)
- Mechanical diode one way clutch (252mm)
- Multi disc clutch pack (265mm)
- 100 square inches of clutch lining (258mm, 265mm)
- Billet front cover on every diameter
- Furnace brazed and hand TIG welded
- Torrington style bearings
- Flanged impeller hub for anti-flex durability
- Hand assembled to exacting tolerances
- Custom manufactured in the USA
About Circle D Specialties: Circle D Specialties has been building torque converters since 1976, growing from a Houston auto repair shop into one of the most trusted names in performance transmission technology. Using CFD modeling, SolidWorks design, and 5-axis CNC machining done entirely in-house, Circle D custom tailors converters to match each customer's exact combination. Their converters have powered record setting drag cars, including the Silver Bullet, which set the world record for fastest naturally aspirated S550 Mustang, alongside a wide range of high horsepower street and race builds.
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