E30 325i buzzing/whining

Hello All!

in my 1991 E30 325i i hear a distinct buzzing. It is like it is a heat shield but the more i listen to it the more it begins to sound like it is rotating. I think it is the transmission, but i am not sure. it seems to do it any any tempreture. it mostly happens during acceleration between 1500 and 2500 rpm's. recently it also started happening while idling. sometimes if i shift to neutral (its an automatic) it stops, but other times it just makes the buzzing quieter.

at times i think it maybe the exhaust since i have a hole and need a new one, again i think this since it sometimes sounds like metal viberating.

any help or ideas would be greatly appreciated, i wish to keep the car in top shape!!

thanks!

Also, i jsut would like to add:

around last december i went to jiffy lube ( where i will never go again, they are terrible) and asked them to also change my atf fluid. they overfilled it and it burnt off and such, but is now to a seemingly normal amount of fluid. the main thing i am worried about is the tranny, dont want to bust it or anything. I have heard that both adding too much atf is bad, and als have heard that it wont hurt anything, it just may cause a fire. i heard that it was bad because it will bubble up and be useless to lubricate the tranny. which is true?

thanks again!