In Subaru TR580 transmissions, the TCC control valve controls the apply and release of the torque converter. The boost valve and sleeve assembly receives fluid signal from the control solenoid and reacts on the control valve. This shuttles the control valve to its full stroke position, where the converter apply circuit is opened and the release circuit is vented. This moves the torque converter into lockup position. Bore wear around the TCC control valve reduces converter and lube flow, while boost sleeve wear causes overheating, fluid loss and prevents converter lockup.

Reconditioning the bore and installing Sonnax oversized TCC control valve and boost valve kit 823740-01K restores hydraulic integrity for proper control of converter apply and release.

• Hardened carburized steel valves combat premature wear
• Oversized valves maintain OE pressures