525i e34 auto. trans noise..help!!

[m50werx]

hi
new on here as of now. i own a 1996 525i se auto. bought from my father who owned the car from new and meticulously maintained it and now replaced with an e60. the car is mint and has covered 177k and was driving perfectly until 4 weeks ago. it has developed a whine from the the gearbox that did come and go but is now there all of the time. i am a motorcyle techincian so understand the workings of the system. i have tracked it down the bell housing on the gearbox input section. its worse when its been stood for a few days and im now very concerned. it still drives/pulls and shifts the same but has a noise similar to a worn half shaft on a front wheel drive car/van.....any helpers out there????? im guessing its a input shaft bearing or similar? are these known for it . the trans oil has not been touched since 90k

many thanks