Low speed , it is quiet, higher speed , rattles, I balanced the
wobble out of it years ago, have a 18" down shaft on the fan, checked
the blades, pushed up and down on the fan blades, arms, in the
center of the motor and have the play there.

There should be some axial play. Those are simple thrust bearings.
"Rattles" don't come from axial play, unless it runs so fast it lifts the
fan up by aerodynamic force (not likely).

Even the cheap Hampton Bay fans from Home Despots run nearly forever, if
they're balanced. (with the exception that if you regularly smoke or cook
near the fan, the bearings may get gummed; and if so, solvent cleaning
and re-lubing will fix that).

If you've got a rattle, it's almost a sure bet that 1) the fan is still
slightly out of balance, even if you don't see the wobble, and 2) that
some escutcheon bell or plate is jiggling around slightly loose. Those
are about the only parts that would make a true rattling sound. You
would perceive a 'rattle' in the main spindle as a lower-toned knocking.

Lloyd