Cone-style Sure-Grips are worn out when the cone clutches bottom-out in the case. To inspect this unit, the differential was dismantled and then reassembled with some clay at the clutch-cone ends to gauge the remaining clearance. We found .060 inch, which indicated plenty of service life left. If the clearance is near or at zero, the clutches won't grab, and the limited-slip function will not work. Machining the cone ends and adding spacer shims behind the side gears can breathe new life into a worn cone-clutch Sure-Grip.