Probably the flex disk at the transmission end. This can easily be verified by jacking up the car and examining the driveshaft. You will know if the flex disk is bad. It will be loose back and forth.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T