This transmisson leaks slowly over the years. If there was a dipstick and filler tube no big deal but with bmw no such luck. If you are going to top up the trans fluid (which should solve the majority of the problems I read about the trans) go ahead and drop the pan, new filter, gasket fill fluid with car LEVEL then reset the trans
turn on ignition (not engine) with foot off brake
put gas pedel to the floor for 60 sec (helps if radio etc is off)
listen for clicks
Trans pefect ever since
Make sure when you fill with fluid you put in all 9(i thimk) liters.
Found Two filters for that trans and one fill tube was lower than the other, that means less fluid