Rear Hub Shakes

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.

yeah my experience is that the axle will pull in and out as well. the calipers kind of dumb down this feeling though, so i was wondering if maybe he had it off and thought that the feeling was excessive.