Check the camber of both sides to see if one of the rear end tubes is bent. There are a couple of ways to do that at home, both requiring a flat surface for the car to be sitting on.

First one is to use a carpenter's square and check against the sidewalls of the tire. Make sure that you are either in front or behind the bulge at the bottom of the tire.

Second is essentially the same but using an electronic level (Smarttool) and a short straight edge, again across the sidewalls of the tire to one side of the bulge. This is more accurate and gives you an actual camber reading of each side. It also allows you to compare side to side when on a surface that isn't level.