No screw or grub screw broken. Took male and female parts apart, Diff balls were ok, looks like no wear, lots of diff lube still in the Diff, put some more in anyway. Tighten the Diff and placed in back in the cat, checked grub screw and screw were tight and wasnt sliping. Tyred it again and it seems fine
no sliping or anything, it is now a diff. So strange
Am racing tomorrow so will find out if the diff stays that way
Will let you people know