Check flex discs or center support bearing. Drive shaft does not go "out of balance" per se..It will create vibration if it isn't running true. The only way it can go out of balance is actual physical damage.

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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.