In GM 4T65-E units, continuous oscillation of the converter apply valve in the cast-aluminum bore causes bore wear, particularly at the TCC signal valve spool closest to the solenoid. Wear in this area allows TCC signal oil to leak, which inhibits the valve from stroking to the lockup position. Due to the valve body casting design and oil flow, this valve is also subject to extreme side loading, which increases the wear rate. Early OE versions of this valve were made from non-anodized aluminum, and show significant wear marks. Reconditioning the bore and installing Sonnax oversized TCC apply valve kit 84754-50K provides a positive seal and ensures proper valve stroke.

• Hardocat anodized aluminum valve combats premature wear
• Annular grooves help keep valve centered and improve performance and prevents side loading
• Re-use the OE spring
• A replacement O-ring has been included for the OE end plug, to be used after inspecting the TCC regulated apply valve