Recently I replaced the bearings in the rear end of a 1996 Explorer. I replaced the bearings, due to having play (in and out motion) on the driver's side. This fixed the play on the driver's side, but it is now on the Passenger's side. (both sides were replaced at the same time). Does anybody have any idea as to what might be going on? I just wonder if spider gears could be worn, or if the pinion gear in general needs to be re-shimmed