Circle D GM 258mm Pro Series 8L90 Torque Converter

Circle D Specialties GM 258mm Pro Series 8L90 Torque Converter

The Circle D Specialties GM 258mm Pro Series 8L90 Torque Converter is a highly versatile, high-performance upgrade for enthusiasts running an 8L90 transmission in their modified GM vehicle. The 258mm (10 1/4-inch) diameter offers a perfect middle ground—significantly reducing rotational mass for rapid throttle response and quick acceleration off the line, while maintaining slightly more surface area than our 245mm option for excellent streetability and efficient torque transfer.

Engineered to deliver massive value and handle serious power, this Pro Series converter features a rigid billet steel front cover and a billet apply piston to completely eliminate flexing and ballooning under heavy torque loads. Crucially, it utilizes a Triple Clutch Lockup assembly, providing unmatched holding capacity during wide-open throttle (WOT) shifts on modern 8-speed applications. Inside, heat-treated steel splines and a flanged style hub ensure superior anti-flex durability, while the assemblies are fully furnace brazed with hand TIG welded fins. For builders planning to use aggressive power adders, an optional Heavy Duty Upgrade is available, adding essential additional balloon plating on the impeller along with heavy-duty welding.

Key Features & Upgrades

• Designed specifically for GM 8L90 transmissions
• 258mm (10 1/4") diameter delivers a superior balance of rapid engine response and streetable torque holding
• Triple Clutch Lockup for extreme holding capacity during wide-open throttle (WOT) shifts
• Rigid billet front cover and billet apply piston prevent flexing and ballooning
• Optional Heavy Duty Upgrade: Adds additional impeller balloon plating and heavy-duty welding for extreme applications
• Heat-treated steel splines and flanged style hub for maximum durability
• Fully furnace brazed internals with hand TIG welded fins
• Hand-assembled to exacting tolerances for dominant track performance

Specifications

• Application: High-Performance Street/Strip Torque Converter
• Transmission Compatibility: GM 8L90
• Converter Diameter: 258mm (10 1/4")
• Construction: Billet Front Cover & Apply Piston, Furnace Brazed, Hand TIG Welded Fins
• Lockup Type: Triple Clutch
• Hub Style: Flanged Hub with Heat Treated Steel Splines
• Options: Multiple Stall Speeds (2800 up to 3700 RPM) and Heavy Duty Upgrade available

Notes

• Custom manufactured product built to your exact specifications.
• Estimated lead time: 3-4 weeks.