Well my Cobalt has been making a clunking noise whenever I would slow down from a reasonable speed. It first started as a clicking noise, then it has progressed to a more clunking noise. It seems to be coming from the dash, or behind it. I have already looked under the hood to see if anything is hitting/rubbing and found nothing. Besides the noise, the car seems to be running fine, starts up, drives and brakes like it should. It is an 05 sedan with basic bolts on's and sportlines. Any suggestions to what the noise would be?

 

I would look at the engine mounts or the exhaust.
The cat could be hitting caused by engine movement .Take a look underneath for signs of something
hittting.

 

I didnt think it would be the cat, it doesnt happen when I'm in park, neutral, or reverse. Only seems to happen when I'm at a reasonable speed, when I'm driving. The only thing I can think of right now is that the wheel liner on the passenger side is vibrating when I'm driving (it is missing a few clips) or the front lower air damn (plastic that hangs below the front bumper) is loose and vibrating with the wind.