I just came from having a new door check put in my 260E and have developed the same squeek you are referring. My mechanic seems to think it is the "rear carrier support bushing" and to drop the axle pays 7.9 hours, plus the time to r&r the new part!
Mine doesn't appear to sit any lower than what I would call "normal" and the Bilsteins are about 4 years old, so I'm good there.
Decision time, as I'm not sure I want to sink that kind of money in a 15 year old car with 301,000 miles. What to do; it is also my daily driver. I'll probably live with the squeek until spring.
How would you go about selling a car of this age/mileage?
01 S55 AMG Silver
01 CLK55 AMG Silver