Rear Hub Shakes

It's been happening for some time now. About 2 weeks ago the passenger rear wheel made a clicking noise when I made left turns. I took the rim off to see if the brakes had too much play in them and they didn't. For the past 3 days now it does it how ever I drive. It's annoying. I took the rim off again and found this. Here's a video. What's the problem and how do I fix it.

YouTube - Shaking In Hub
 
From that video it doesnt really look like anything wrong from what i can recall. Are the calipers still on when you took the vid, i couldnt tell? the noise you hear is from the rotor clanking on the wheel studs and when you place the tire on, it locatesand snugs the rotor in place.

Also when is the last time its had a brake job the star washers are still on it? usually those get removed, even when a big name shop replaces brakes.

My rearend clunked and made a weird noise on my cobra when the differential fluid was changed and no one put the friction modifier in.

you should be looking for axle play in and out( possible c-clip failure). up and down(bad bearings).

this atleast gives you some things to think about and start with
 
Every Mustang I've ever owned had in and out play on the rear axles. I believe this is normal. There's no way to keep them from going in and out because of the C clip setup. If the C clip fails, won't the axles come right out of the car? I know they do on Fox's because of their drum setup. I guess the only thing to hold our axles in at that point will be the rotor/calipers.
 
I'm gonna take the brakes and everything apart tomorrow in hopes I will solve this. I took the wheel off again and now it is louder after I put it back on. I think I may try some troubleshooting by rotating my tires see if it's the wheel. Not sure but that's one thing that's worth a shot.
 
Here's and update with a solution in case anyone ever comes into this problem.

After toying around and taking the whole thing damn near apart, my friend leaned against the car and it made that noise. Turns out it's nothing to do with the hub, wheel, brakes, nothing. It was the exhaust. The mount had come loose and was hitting a bracket for the impact bumper. Tightened it up and took it for a spin, swerved right to left trying to recreate the noise, and nothing. So it is fixed. Gonna go get some new rubber mounts tomorrow since a couple of them look like that are about to fall apart.