What would cause vibration in drivetrain when ideling in gear?

Engine/transmission mounts are the usual suspects.... If fact 'more' than likely!!!!.. Car is 21 years old so.... Have a good independent shop/mechanic check it out... Nowadays them kids at the dealerships can't figure out a forked stick if it ain't a pic on a computer screen, sent from the factory!!!!.. Contact the shop listed in answer # 2.... Seems to be in same area... Click on their shop name to see reviews here on RepairPal...!

I second Pushrod, most likely it's one or more mounts are broken.

Check the engine and transmission mounts. When was the last time the engine was tuned up?