Quote: Monty I don't buy it, I will buy the case flexing and allowing the pinion to try to climb the ring gear. The large pinions break ring gears just like the small ones do. So I guess they flex too even they are bigger than most 9". If they flexed that much we'd see broken pinion shafts.
UUUhhhmmm, a Ford has a support bearing.......so how's it gonna flex. Not wanting you to "buy" it, don't have to sell it to you, because it's a fact. There is not enough room in the case to actually break a pinion off from the side load.......BUT......you ever had a broken set of gears magged. How much YOU willing to bet on the pinion NOT bent or cracked, because I will put a wager that it IS.
Monte
I fully understand the extra bearing on the 9" and I'm willing to add the extra material cast into the case for the bearing helps in the strength too. Yes I have broke an 8 3/4 and I full well know my pinion is broke. I can see where the teeth were that are gone now . I'll chuck the pinion up in my lathe and see if it's bent.
I'll stick with my opinion that a stronger case and the third bearing are where the 9" has the strength advantage over a 8 3/4. Not pinion shaft size. I agree to disagree, Merry Christmas .
. I'll chuck the pinion up in my lathe and see if it's bent. 
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