I have had a constant mild jumping/hopping in the rear end of the truck. I suspected a left tire as it was hopping quite a bit when run with the wheels elevated. I did not try that wheel on the right side.
I did a rear brake reline and did not turn the drums. When I adjusted the shoes I could not get a constant drag on the drums when I turned the wheel by hand. It would drag and run smooth and so on.
I thought that either the drum is out of round or the axle might be bent. And seeing how I had a bouncy tire I started to think the whole problem might be an axle.
There is no sign of seal problems on that side and when I tried to balance the wheels that particular tire was way out of balance and would have taken too much weight to rectify.
I thought when I posted that perhaps if I could check the axle with some type of indicator then I could hopefully rule that out as a cause of my hopping.

1949 Chevy 1/2-Ton
"Sedgewick"
In the Gallery
1989 Caprice