I have a 2011 3.6R that I put H&R springs on it about 10,000 miles ago. When I first got them on, the front left corner would make a quiet popping sound when turning left at slow speeds. Never really figured out why, but someone recently posted that theirs did the same thing and they just had to adjust the spring to sit in the bottom. I planned on doing that over my holiday break. Then my rears started to make a similar sound but way louder when I pull in or out of an uneven surface like a transition into a driveway.
So this past week I pulled all my wheels off and adjusted and tightened my fronts and they are now quiet. I could see anything wrong with the rears. They were all tightened down and had no play in them at all. I checked all my bolts on my sway bar and everything else back there and all seemed well, but still makes a scary sound to me.