I agree with your post. But I was trying to emphasize stiffness and rigidity to maintain mesh alignment. Not outright breakage.
Most of the breakage I have seen is cap breakage and gear breakage. What other kinds of breakage have you seen.
As you posted most of the time they shuck the teeth off the ring and pinion gear or break the cap on the pinion side.
A 9" is a good design but unless they are in a good nodular case with a good pinion support they aren't really that strong either. My brother and I broke several in four wheel drive trucks years ago, it ruined the case every time.
