00outback

Ok so my wifes car is an 00, Legacy outback, 2.5, auto. The car gives us a hard time getting into first, but once it finaly shifts its fine. I have read that this is a common problem with these vehicles, is there anyway to fix this issue without getting the trans rebuilt? Last week the car left the wife stranded at her work, I did a fliter change and a fluid change. ( it was not a flush just a change so there was still some old fluid in the converter) This worked the car was running beautifully for a week and yesturday it started the same crap again.