story goes :

     1650  driving home with wagon into... slows to a stop at the  bottom of a hill...  motor fine... clutch fine... tranny fine.
drag it home  and  find  coupler slides   off end of  engine out put..

parts book lists no  snap ring, or other way of keeping  the  sproket on the shafts...    why has this started?   what can be done?   

we are  puzzled?