Save yourself a shit load of time and frustration and message Vinnie so he can explain to you what he went through and finally just put an aluminum DS under his car and solved his issues. It is a known phenomenon and either a carbon fiber ($$$) or aluminum DS will solve the issue. Vinnie's solution was by far the best one I have seen.

http://www.foxtbirdcougarforums.com/...crown+victoria

http://www.foxtbirdcougarforums.com/...um+drive+shaft

http://www.foxtbirdcougarforums.com/...um+drive+shaft