Clamp Nut removal tricks ???

Hi Folks -

Have 25 yr old beauty - stacking W/D, replaced lots of parts in dryer,
but now the washer won't agitate.

Currently I am trying to get off the clamp nut
** HAve the 2nd best spanner wrench
** sprayed WD 40 all over
** using a 10# (5?) sledge and after an hour,
the nut has not moved
** Also used a metal rod to bam the sucker,
on several sides - still no luck

any suggestions ?

--> soak in WD 40 for 3 days ??

Tia,

Still Trying III