Cab, I am sure you are right about the crush sleeve. I raced an 8 3/4 for a short time until I was traded an OEM Dana 60 for a B-body by the yard owner. Out came the 8 3/4 and in went the Dana and I have never raced anything else and they all had solid spacers. When I worked at Eastside Auto Salvage, we took in a W100 that had flipped when the pinion nut loosened and the 9 1/4 rear locked up. I have seen the "Gorilla Nut" replacement that also fits the Dana 60s. Very impressive for a nut!