Wheel bearings?

If it was a chipped tooth , I would expect it to happen whenever it was rotated, even with the weight off the rear wheel/jacked up. It doesn't though.
Like I said, hope it's not but going to have to check all related parts so being that close I'd have to check for piece of mind.
 
"U" joint ??????

Tried it with the swing arm in various positions including jacked up w/ no weight on it. only does it when it's under it's own weight or more. Would think a bad u-joint would do it regardless when it's rotating.