Welcome to the forum. There are a number of good suggestions in this link that may help.

http://www.peachparts.com/shopforum/tech-help/178790-1990-300e-m103-clunk-when-shifting.html

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles