[AT] JD60 Flywheel

[D. Day]

Several months ago my '52 JD60 has starting shaking. The steering shaft 
vibrates and even the rear tires have started shaking.  Now today, I noticed 
that the pulley is starting to shake a little.  I'm pretty sure the flywheel 
is not positioned correctly on the crankshaft.   Is it common for flywheels 
to move after a while?  Is there an easy why to tell if it's where it should 
be?

Thanks

Dick Day