[rchippie]

I have the same problem. i bought 60 set screws from tonys screws, so i can replace them every couple times i take them off. I personally think the tips of the set screws wear out from being tightend so hard agaisnt the pinion shaft. I also put a little extra red locktite on. So it runs around the pinion shaft & the inside of the drive cup. I think it will kind of act as a glue and help hold the drive cup on.