Thanks, Mike! I did a search for "rear control arms" before I posted, but didn't find what I was looking for. Your key words on "floating" led to a good thread. I don't have any of these symptoms yet, but still wonder of there is a rule of thumb on preventative replacement.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E