why a Ford 9"?

72goldduster said

DEFINITELY NOT TRYING TO OFFEND ANYONE WHO CHOSE ONE, but what are your reasons for it? the 8 3/4 is much stronger, has bigger everything (except of course, the ring gear diameter, and in the 741 case the pinion diameter). again, not trying to get anyone hot headed, I'm just wondering what made you choose a 9" instead of the tried and true 8 3/4"

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Hmm. 8 3/4 much stronger? There are legions of drag racers out there that would beg to differ. History is not on your side here and the opposite is more likely to be true.

8 3/4 has bigger (almost) everything? No contest to the pinion diameter, but the Ford 31 spline axles are superior to the 29 spline Mopar axles. 9" is bigger than 8 3/4 inch although some Ford 9 " rings measure 8 3/4. The 8 3/4 pinion in the 489 case is actually bigger than the Dana 60 pinion. (1 7/8 vs. 1.626.) Interesting that the Ford 8.8" shares the 1.626 pinion size with the Dana 60.

Some of the other comments thrown out here are also worth mentioning. Ford 9" a copy of the Mopar 8 3/4"? Both introduced in 1957. Nothing to see here folks, move along. Rolling resistance? The small Ford pinion is the only factor likely to make a difference here and that would be in Ford's favour. I suspect most users would not detect the difference.

Keep your Mopar all Mopar? Definately a point to the 8 3/4. Still, the Dana 60 is the "ultimate" Mopar rear end and a common source for Dana 60 housings would be 3/4 ton Ford trucks. Hmmm...

I would not go out of my way to put an 8 3/4 under my Cuda, Reason is the high cost, poor availability, and 4" bolt circle of the A body piece. The 8.25 found in 73 and later A bodies is a bolt in, has the LBP and is plenty strong for street use. If I was to use a non mopar axle, I would be looking seriously at the Exploder axle. Best wow factor is, of course the Dana 60. I might just modify a Ford truck piece with LBP axles and try to pass it off as Mopar!