Kenmore laundry center stacked washer/dryer washer tub shakes almost violently on spin cycle.I may have changed setting during spin cycle.Tub is off balance.The appliance cabinet is balanced and on a solid floor. It was professionally installed.I have experience with opening up and looking inside.Haven't opened the cabinet yet. I have the exploded parts diagram. I see the snubber ring, seal assy,washer and transmission washer and spacer bearing block,on the diagram.I don't know what to look for first non what to do about it once I set aside a couple of days to open the machine and look inside.Help is much appreciated.