I'm pretty sure this sound is coming from my tranny. It sounds like a washing machine with a bunch of metal buttons from your clothes hitting the bottom of the machine at each turn. It was also leaking really bad, I just drained it and dropped the pan, and am considering either putting it back with a new gasket so I can still move it around without making a mess on my driveway and garage, or dropping the whole tranny right now and saving up to get it rebuilt as soon as I can. I'd be taking the tranny by itself because the car is not yet registered.

This sound occurs at idle, in park.

 

Maybe the flexplate?