I put an 8 3/4 rear in my 86 RC 2wd with the last few years that had the 5 on 5 1/2 pattern axles(72 through 74 4wds?).

I'm now running a Dana 60 8 lug rear with 8 lug(heavy 3/4 ton front end) up front....all from an 85 2wd 1 ton. NOT that the 8 3/4 failed. I just like lots of woe...with the bigger breaks....lol.

I'm not a fan of the 9 1/4.....it seems that I've seen more of them being replaced than 8 1/4s......but what causes them to fail......who knows.

As in was it operator error......like taking them under water or letting them leak until there is no oil left, again my two cents.....which around here doesn't mean much. LOL