one other thing that comes to mind here..look at the threads and how far they go down thru the pinion yoke..if your threads stop on the top side of the pinion yoke you will need a spacer...
i am just hoping someone didn't put that yoke on without checking the pinion threads coming thru the yoke..when you pull it off please check this..it could explain why the 1/4 spacing is there..the yoke could be playing forward without the shim in place...the shim is about 1/4 inches exactly..
let us know.
and when you go to put that yoke back on,,give her a good thick layer of loctight red and hammerback down
Brian