So last week the Temp. dropped significantly and i'm hearing a rattling from the rear of my car. i have the 25mm Hotchkis sway bar and i was greased a few months ago. Could the cold cause the sway bar and bushings to contract enough that there is a gap causing it to bang around?

 

I hear the same thing. Its really only on the first like 4 bumps i hit coming out of my bumpy road. Then it goes away. I have a 19mm bar, but same thing.
I'm using the WMW zerk bushings

 

Check your endlinks, the end connecting the link to the sway bar. That has to be pretty tight, otherwise they can bang against each other and create noise