March 21, 2013
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.
Always inspect the TCC regulated apply valve for wear. The O-ring in this kit should be used to replace the original end plug O-ring after inspection. Worn valves or bores can be repaired using the Sonnax TCC regulated apply valve and sleeve kit 84754-34K.
Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.