4L80E/4L85E Transmission TCC Regulator Valve Kit Symptoms: Burnt converter Converter shudder TCC apply & release concerns TCC codes Cause: TCC regulator apply valve wears the aluminum bore, causing loss of converter apply pressure oil. Correction: This TCC regulator apply valve kit with a hard-anodized aluminum valve with PTFE seal prevents valve bore related problems. Some vehicles with a 4L80-E transmission may exhibit the following problems: converter shudder, burned converters, no TCC clutch apply, and/or code 68/39 or P1870/P0741. Often these complaints can be caused by the constant oscillation of the steel TCC regulator apply valve wearing the aluminum bore, resulting in a loss of converter apply oil pressure. Sonnax offers a replacement TCC regulator apply valve kit 34994-01K that will prevent valve-bore related problems. Hard-anodized aluminum valve incorporates a PTFE seal at the main wear area of the bore to prevent oil loss. The valve spool land at the spring end has been lengthened to provide greater bore-to-valve surface contact, thus further preventing leakage. The heavier spring provides OE lockup feel. The lighter-duty spring provides a firmer lock-up, best suited for towing applications. The valve spool has annular grooves to help center the valve in the bore. A .030" chamfer has been added to allow more line pressure into the TCC regulator apply circuit to prevent converter shudder.