February 21, 2013
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. Installing Sonnax TCC regulator valve kit 34994-01K shores up the hydraulic integrity of the TCC control circuit to return robust TCC operation.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.