So I dropped my 09 g37 rwd on Tien Street Basis coil overs. All went well for a month or so then I began to hear a clunk in the driver side rear. It is intermittent. Once it got really bad, drive to my shop and it had stopped by the time I got there. They lifted and could not figure it out. When it is happening I can stop the car and reproduce by pushing the bumper down on back passenger side. Any ideas? If I get up to free way speeds it goes away for a while. Very odd.

 

Either you need a touch more preload or the top bolts are loose.