as you know the 246 and the 315g do not interchange. assuming you have the right u joint, if there is no grease zerk they are packed with a lot of grease, compressing in a vice might force enough grease out to get the clips in, but first, move the joint from 1 cap to the other, if it seems to go deeper into one than you laid a roller bearing down in the cap, just thick enough to give you problems.