we really do need a video of this.
or a very good description.
are they jiggling from side to side, or up and down? is it both? what is the extent of the movement? small, like the ripples on a still lake after a small stone is dropped? undulating, like a roller Coaster?
it could be that your motor shocks are worn out. there are two, and they don't really hold the motor still as much as they "calm" the resonance of the normal vibration of the motor.
John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!