I recently lowered my car with springs and installed yellow Koni struts/shocks all around. They were fine at first but now the rear upper mounts squeak inside the car like crazy. I've tightened them, loosened them, and they still squeak. I sprayed wd-40 between the isolators and the body and that fixed it for about 15 minutes of driving before the squeaking came right back. HOW DO I GET IT TO STOP!?? It's about to drive me crazy.

 

I had this same problem, but only on the passenger side. If it is the mount, make sure the rubber bushings are installed right. Top and bottom.

Also consider your lower control arm bushings. I swore up and down it was my upper shock mount squeaking until a friend rode with me to listen. That's when we found out it was the lca. Replaced them with aftermarket from Founders, and now no noise.

 

I'd suggest looking REAL CLOSE at those "mounts" (holes in the sheet metal), make sure the metal isn't cracked around them. That's how they ALL fail, sooner or later.