Fastner Question

Why the slots in this nut which is original from a rear spring shackle/hanger. I assume it has something to do with gripping better to bolt and prevent unwinding but not sure.

I notice now many aftermarket spring hardware comes with nyloc nuts instead of these slotted nuts.
Yes, the Nylon locking nut is an updated version of the old lock nut.

View attachment 1715569857
Yes, the nylon lock nut is an updated version of the lock nut.