The pre-1988 XJ6 and the XJS have a problem with the outer hubs on the IRS unit. The lower pivot point has a tendency to crack (definition:The rear hub is the big aluminum unit that the rear wheel bolts up to). Check these periodically, cleaning them up if necessary in order to see clearly. A cracked rear hub can fail at speed, which would be a bad thing.
See our Jaguar Parts Store Catalog to order parts.
