I know youtube has some good vids on what a bad u joint looks like. Good thing is they're pretty easy to replace if thats the problem

 

I haven't seen the video's but you can jack up the rear and look for play in the joints or if there is red (rust) dust on the joints it is a good indication that they are bad.
good luck..

 

Sounds like a broken belt in a tire to me.

 

Ive never heard of that, is there any way to check for it? If the u joint is fine ill look at this next

 

Bulge on the tire is a broken cord. Usually at slow speed in a smooth parking lot the vehicle will crab walk side to side.

 

You can jack it up and spin the wheels. You will see one that is out of round fairly easy. Usually a broken belt will be the cause.. And yes, you will usually feel it have a bit od a wobble at slow/idle speeds as well. Shoot, you might also make sure all of the lugnuts are tight since you just bought the thing.