Looking at my 2008 f-350 4 wheel drive, there are loose plastic rings around the front axle in-board of the u-joints.

Are they supposed to be loose? Did they break off from a dirt seal?

 

those are probably the outer axle seals.
not really needed, because the real axle seals are inside the tube at the differential. all they do is keep dirt out of the tube when they are in place.

on my 02 they have been hanging in the air for the 10 years i have owned it

 

Thanks, that's what I had hoped.