My rubber isolators are on the bottom coils. In fact the start a few inches up from the pocket on the spring perch of the strut on the spring. Did you re use the stock struts and strut mounts? How much do you spring drop the car? Does the noise come from both sides or just one? Does the front end make noise when you turn the steering wheel?
More than likely its the dang strut mounts? There POOP! One time use only. If your missing even 1 ball out of the bearing pack in the mount noise will occur. The spring rotates as it compresses. The only place it can rotate is at the upper mount. Pull the strut assembly out and have a look-se. Get you self some shocks/struts/strut mounts soon too
2013 5.0 m6 base 3.31's tint 20in Shelby razors 255/35/20 falken fk 452's koni srt.t's sr springs j&m phb gt500 mounts upr rear billet lower ca's upr brackets upr adjustable upper ca flowmaster at classics steeda cat deletes airaid cai premium st brace jlt catch can MGW shifter and blk ball. Currently bama tuned 400hp 383tq. Zex blackout kit w/msd digital window switch, fpss, zex bottle heater, bottle opener, blow down, and purge with a dyno tune coming soon..