Problems with the Dart Continue

So as some might remember, just this week I finally got my Dart back on the road after having the rear end replaced.

The day I picked up the car I noticed that when I put the brakes on the car pulls to the right. Also there was a shimmy that wasn't there before. I thought it was one of the rear tires out of balance.

Went on a long cruise today and when driving, the shimmy was so bad that the steering wheel was bouncing left and right and when driving slowly, you could actually see the entire car rocking back and forth.