What did I do wrong?

1969383S said
Swapping gears in my 742 case! Pulled the center and removed the 4.56 gears. Installed new koyo pinion races and new 3.55 pinion with koyo setup bearing. Ran the pattern and got the pictured. Looked good to me. So I do the pinion freeze and bearing heat and it dropped right on! Happy and go for re-assembly and darn the pinnion is dragging on the center section! What happened? I recheck my backlash and it still hits. So I make the descion to press off the pinion bearing thinking there is a race issue. I put the set-up bearing back on and still have interference. I removed the races and confirmed they were seated and no obstrutions. Installed new races again then reduced the shim by 10 thousands and get a good pattern. I am concerned that only reducing by .010 might lead to contact at temp. Opinions?

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Had this same issue last year with the pinion gear contacting the carrier with a fellows 8-3/4 --- tranny shop could not figure it out ( they ruined his original case trying to make it work ) and it ended up with me to sort out --- gears were Doctor Diff brand 3.55 for 742 case --- what I did was remove .030 off the pinion face ,,, this does not compromise the gear or contact pattern at all --- no issues after that, gears set up ok ( with .095 shim ) with plenty of clearance for the carrier .