Every few years I bleed the clutch on my E-150 van, this time I went a bit too long, and getting into first gear when things heated up was getting a little tough. Anyhow bleeding corrected the issue. What I found interesting was between the bell housing and the rear of the engine, at the bottom of the bell housing/engine there's a small space, which had what looked like mouse fur and bird feathers packed in, I removed quite a bit. I'm 99.9% certain of what it was, I doubt it was a rat. I could see how a mouse could enter, there's enough space going into the M5OD transmission from the line which feeds brake fluid to the slave cylinder. A mouse could easily get in, just by the way it's designed. But bird feathers were packed in with the mouse fur, I doubt a bird flew in, or a mouse attacked, killed, and dragged one in...........