I think age also is a factor. My '86 300E had 67k when I bought it in 2002.

I noticed that it was fishtailing and when I inspected the rear links, the rubber was craked on the control links. Also, the rubber in the differentil mount bushings had deteriorted. I went ahead and replaced all the links on the rear end and the diff mounts also. I also replaced all four sub-frame mounts. The sub frame mounts had no elasticity in them and were craked pretty bad.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold