Would suggest checking the vibration dampner, have seen similar failures on IH engines. Damper hub and pulley are seperated with a rubber ring that fatigues allowing the hub to spin inside of the pulley. Check fan pulley for wear on one or both grooves. Contact your CASE IH dealer about a larger rotary screen shaft and bearings in kit form that has a larger screen mounting plate to prevent screen vibration. Many years ago there was a mod program that addressed some of these issues. Check plenum for air leaks that are not going through the rotary screen. Check the air screen brush and check to see if rotary screen is round and if the rotary screen fan still has all of it's blades