If she clunks or thumps, or, jumps a bit when accelerating (especially from a dead stop) I would suspect either the center bearing or the drive shaft itself. On my '88 750 it was the shaft that was bad but on some the center may be the culprit. The Bentley is the bible for service and i have never seen one at Barnes and Noble or Borders, bought mine from Amazon online, may also find them on Ebay, in eityher case, there is a wait.