I just got done with mt Tremec 600 swap. I was inspecting and cleaning my old Spec Stg 2 clutch 'cause I was planning on selling it on Ebay. Upon closer inspection of the disc, I saw that the disc itself was cracked. I'm not talking about the friction material, but the actual metal backing of the clutch. Needless to say it's going in the trash now. I have to think that this would have eventuallly led to a more serious failure. Just a reminder to always closely inspect any parts before using or re-using them.
