[big gear head]

All of the factory installed Eaton Posi units in the 12 bolt and 8.2 10 bolt had steel clutches, 18 discs and 200 pound springs in the standard units and 22 discs with 800 pound springs in the heavy duty units. After market Eaton Posi units today have carbon fiber lined clutches, 14 discs with 400 pound springs. The Traction Lock differential in the 8.5 corporate 10 bolt had steel clutches. GM used the Auburn cone unit in some of the 8.5 rear ends and all of the 7.5 car rear ends that got the limited slip differential. Starting in '90 the 8.5 in the Impala and Caprice got the Auburn. The truck Eaton locking differential had steel clutches until sometime in the '90s I believe and then went to the carbon fiber clutches. All of the old Chevy '55-'64 rear ends with limited slip had steel clutch plates. The Buick, Olds, Pontiac 8.2 rear end had cone Borg Warner differentials. The '04-'06 GTO also had a Borg Warner cone differential. Torco oil is the only oil that will work in these GTO rear ends. GM has been dealing with steel on steel for a long time.