Transmission Problem? 1999 Subaru Legacy 30th anniversary edition?

has anyone checked the transmission modulator valve? pull the line running to it if you see fluid in the line or any comes out replace it. this is a vacuum port and shouldnt have any fluid in it. my dad taught me that and i had to change the one on my nieces old pos mustang she limped to college(84 4cylinder model what a clunker!!!!)>