If you have an old snapper riding mower and recently when you put it into reverse there was a squealing metal on metal sound that happened for awhile and now it is doing it in the forward speeds i?

The rubber around the outer edge of the driven disc is gone. You will need to get a replacement either OEM or aftermarket, stand the machine on the rear stand bars(remove battery if it is not sealed) and replace the disc. It is 1-0765 without lining and 5-7337 with lining.