GM vehicles equipped with 4L80-E and 4L85-E transmissions may exhibit problems such as TCC shudder, burnt converter linings, TCC apply and release concerns and related codes. These issues can often be caused by critical pressure loss due to excess wear in the TCC regulator bore. Reconditioning the bore and installing Sonnax oversized TCC regulator valve kit 34994-18K restores hydraulic integrity of the TCC control circuit to return robust TCC operation.

• Hardcoat anodized aluminum valve combats premature wear
• Lengthened critical spool for added stability and wear prevention
• Annular grooves help center valve in bore to reduce future side-load wear
• Added chamfer to improve apply characteristics and prevent shudder
• Selective springs; one for OE lockup feel, the other provides firmer-than-OE