The Ferguson TO-30 PTO is retained by four bolts in the housing that holds the bearing and seal housing for the shaft in the rear axle case. There is a snap ring that retains the bearing assembly and it is either worn or came out ofits slot.
Loosen the four bolts and pull it out after draining the 6 gallons of hydraulic fluid from the housing or alternately, putting the front wheels in a ditch so that the fluid moves forward. You can gwet the parts on this site or at your local MF dealer.
You should be asking this question on the Ferguson Forum. You can do an archive search there and get more info. Someone may be able to supply a page from the ferguson parts manual.