September 30, 2005
In GM 4T60 and 4T60-E units, the TCC apply valve acts as the switch valve for converter apply and release. The TCC regulator valve controls TCC apply pressure. Both the apply valve and the regulator valve can cause slip codes. When the apply valve is worn, it often returns to the unapply position even though the TCC apply solenoid remains energized. Generally the apply valve causes larger changes in slip RPM as the converter cycles from apply to full release. The regulator valve causes a more gradual load and heat-sensitive slip. Check for changes in slip RPM with a scanner or changes in cooler flow with the Sonnaflow®. FM-01KA. Installing Sonnax TCC apply valve kit 84754-16K restores hydraulic integrity.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.