Yeah, I've replaced plenty of those. It's where the axle goes into the transmission. I thought it slipped out at first, but they're both locked in. But if you grab the side connected to the trans you can wiggle it around. I've never seen anything like it before. It's not leaking fluid either, so I assume the seals are still good. Just the bearings where the axle goes in are worn out or broken. That's my guess anyway. I don't know what the inside of the trans looks like. As I said, I've worked on cars for over 20 years. I just avoid transmissions. Maybe I need to just tear it apart and see if I can do anything with it. It's already messed up, so what can it hurt?