It is common for the shift shaft seal in GM TH350 and TH350C transmissions to leak. Often this leaking is caused by scoring on the shift shaft itself, preventing the seal from doing its job. Scoring and scratches can be caused by gritty mess getting in past a worn seal, or from using improper tools to remove an old seal. In these cases the shift shaft must be replaced along with the seal to restore normal operation. Fix leaking and messing up for good by installing JSPP shift shaft and seal kit Compatible with 35801-02K.