If the rear control arm bushing (that connects to the carrier) is worn out, then it will start to squeak.
Mine were squeaking and as a temp. fix, I sprayed some lubricant into the joint and it stopped.
I have the rear left and right wheel carriers on my 86 300E out currently as I am replacing all the links on the rear and the rear wheel bearings. I found that the control arm bushings on both sides were completely shot when I pulled the carrier out and I have replaced them.
The part number for those bushings on FastLane is L2030-40235. (This bushing acts like a ball joint.)