The ring should have a bottom out feel to it once it is in, and you shouldn't be able to pull it out by hand once in. To be sure it's in, you could also try measuring the distance from the outer edge of the bell housing to the retaining ring and likewise on the drive. It's about 2 inches if I recall correctly.Not sure what to look for to confirm that the retainer ring is seated properly. Got the bead on the bellows in the groove, then wacked the retainer ring a few times with the retainer driver and 4lb. hammer.