To remove the O-ring, tap on the O-ring using a thin barrel punch and a hammer. This is necessary to check it out.
Remove the O-ring, being careful not to damage the planetary gear splines.
Fix assembly «gear differential housing» using a device (B.VI. 1057), attached to the crankcase.
Remove the body mounting nut.
Remove the bearing pretension shim A.
Remove the entire assembly by pushing it towards the planetary gear.