I know that this thread is a bit old....
the squeaking, creaking, moaning that you guys are hearing in the rear end is from the transverse mounted leaf spring that is in the back. There are supposed to be pads underneath the ends of the spring where it goes into a "pocket" on the outer edges. I replaced mine for like $20 or so and I haven't heard a sound since. My car is a 94 Lumina 3.1L.