Yesterday I was backing out of my driveway and heard a loud "pop" in the rear of the car. I went ahead and drove it onto the road and I kept hearing this strange noise from the rear and the car started shaking. Felt like I had a flat tire so I pulled over.... no flat tire. I drove it about 3 more miles to a friends house and it progressively got worse. All noise from the rear and the shaking. It is a 2WD. Any thoughts?