What is causing the creaking from the rear of my car?
I have a creaking sound coming from the left-rear of my Focus. I can hear it from inside at all speeds whenever I go over any kind of bump, or even just driving through a parking garage. The noise is extremely loud when I am jacking any corner of the car. I even jacked up the left rear and used PB Blaster on every bolt and bushing I could find, to no avail.
So greasing the bushings and whatnot didn't end up solving the creak after all. I just replaced my shocks, and in doing so, found out that what is likely making the noise is the upper shock mount, which is located inside the trunk. This explains why the noise almost sounds like it's coming from inside. I was going to post this as an answer and accept it, but the answer I accepted is close enough, because it probably just needs to be greased.