By 1970, the SureGrip in an 8.75 differential was the Borg-Warner Spin-Resistant otherwise known as the cone type.
It is now produced by Auburn Gear.
Yours is worn out.
The cone type limited slip is officially (per the manufacturer) unrebuildable, but some have cut off the smaller end and spaced in the side gears with shims to gain some more use out of it.
You are sure to get some posts saying it's crap, others saying they have redone theirs.
Regardless, yours doesn't work now, and should be replaced with either a rebuilt Dana Powr Lock or a brand new True Trac. One preferred source is a board member, contact at
www.doctordiff.comR.
