Nick, if the transmount has gone completely soft, then there is a good chance it has separated. This can be checked by putting a jack under the trans and trying to raise it. If the tailshaft leaves the mount, then that is at least one problem that will need attention (easy, inexpensive). The clunk you describe may be the trans case banging the tunnel when you accelerate and apply torque. The last item I would entertain would be the diff mounts. Flex disk is aonther good possibility. Can you be more specific about the noise you are hearing??

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.