I have noticed a definite difference in vibrations from different motor mounts. With poly-filled cheap mounts w/ steel backer plate underneath, the vibrations were noticeably bad. With 1 "Made in Germany" mount and 1 "S11" as in the post #3 link, it idles noticeably smoother. But, I still get a slight resonance at certain rpm's, mostly when driving slowly in parking lots. The engine doesn't visibly move, but you feel the vibrations in the cabin. I do have a poly-filled tranny mount so that might be a remaining culprit.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans