No, there is no rubber piece.
I had an increased amount of noise in the front end when I would accelerate. Looked at the pass side able, and I was able to "shake" the bearing in the bracket. Idk if the bracket and cap our just the cap needs to be replaced when the axle is replaced.
I'll save you the time (i spent weeks looking) Steve @ Tousley (sp) is the ONLY person that has them.
Discontinued by Ford