Do I need special side gears for IRS rear-end??

Can I use a Mustang posi in my TBird, or do I need different side gears to accept the half-shafts??

Thanks!!

yea, they have a machined lip to accept the clip to lock them in place, or else they'll move around some. I asked some idiot to machine me some from a non IRS car and I think the fool lost them, oh well, they can be machined if they are not hardened or something

You need side gears that will accept a half-shaft circlip. Side gears designed for axle C-clips will not allow the half-shaft to lock in place, because the groove isn't located correctly. I don't remember off the top of my head which brands of differentials are circlip compatible, the best thing to do would be call the manufacturer tech line. I can tell you that currently the Eaton Carbon-fiber Positraction is NOT circlip compatible, and requires disassembly and machine work on the side gears to use on the SC. (Believe me, I know all too well about this...) Supposedly Eaton is working on a circlip compatible version.

Does anybody have a set for a 7.5" unit or even an 8.8" unit??

I will buy them or trade you some non-IRS units (28 or 31 spline).

Thanks,
Mike