904 slow shifting into high gear????? Help plz!

I dont see it being in the converter this is the second converter ive had in it and its done it with both. It sounds like im just going to have to pull it and go threw and change all the seals. I didnt air test this one it was bought off a guy that had it redone at a transmission shop. The thing is it was rebuilt probably 15 years ago and never put in untill a year ago.