October 31, 2014
Vehicles equipped with GM Gen. 1 and 2 6T30/40/45/50 and 6T35/31/41/46/51 (Gen. 3 6T40) transmissions can exhibit a number of TCC apply issues caused by bore wear at the TCC regulator valve. Slipping TCC, no TCC apply, fluid overheat and suffering fuel economy are common results of this wear. If the valve becomes stuck in the apply position, harsh TCC apply will be the consequence. If the valve is stuck in the release position, no TCC apply or TCC slip will occur.
For moderately worn bores, installing Sonnax TCC regulator valve kit 144740-38K will restore proper valve function, resulting in proper TCC apply. The valve lands have been lengthened significantly, allowing the valves to operate in unworn portions of the casting bore to effectively seal against leakage. The shuttle valve has been modified to directly engage with the regulator valve, adding stability and guidance to prevent cocking in the bore, which causes the valve train to stick.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.