Leaking 833 Vent

I disassembled the trans when I rebuilt it and never noted a slpask gaurd inside the tail housing so it must have been missing to begin with. I just got the thing installed and really would hate to have to remove it again. What would be the down side of plugging the vent with RTV. Would there be any problem with pressure building in the case, I have no idea where that may come from.