2002 mustang auto:well i noticed 2 days ago that my car make a clunk sound when i started it up. first i was thinking maybe it was in my imagination because i didnt hear it again till late today. it did it again and down the street on takeoff at a light i heard it while first accelerating. not aggressive either sounds like coming from under back drivers seat. i got in accident like month and half ago got used rear axel. but not sure if its that or something else. any ideas? anyone else have this problem

 

Sounds like a u-joint issue. Get under there and check em out.