I searched on this and couldn't find what I was after. I've got a lead on a third member out of an early Bronco (I think) with a gear ratio that I'm after to put under my roadster. The 9" under my roadster is out of a 58 Ford. Any idea if the two are interchangeable? Spline count is what I need and to my knowledge it should work but thought I'd check here first. Thanks Guys.
As far as I know, all Ford 9" rear gears bolt into all 9" housings, the spline count may mess you up, but anything other than 28's is so rare it's barely worth losing sleep over.
And beware that some of the older ones(if you are rebuilding) had a very large pinon seal that has a price tag to match its size.....if i remember right it was about $40-$50 for that stupid thing and I worked at a parts store.
To my knowledge, if you replace the whole third member, then you should be ok. Within 3rd members, there were different carrier bearings and such, but as long as everything gets switched over together, you should be ok. If you switch just the differentials out of one to the other, you may run into problems though.
Ford 9 3/8in 3rd members are different according to Kevin Stang in http://www.kevinstang.com/Ninecase.htm "Here is something else you may run across, a 9 3/8" ring gear housing(sometimes called a 9 1/2" Ford carrier),I don't know much about them, but looking in the book they appear to have come in the larger Lincoln and Mercury vehicles.Note casting number C8AW-4668-B on pinion support and the double ribs(spaced further apart) with the end bent down on one.From what I understand most parts from these rears do not interchange with the 9 inch carriers.I have heard they can be installed in a 9" housing if the housing is notched for the wider gear and the gasket for the 9 3/8" is used (bolt pattern is supposedly the same).I have started to see a few of these in some Ford pickup applications, mainly 4X4 with a trac loc option and FE motors.The truck applications seem to have some better ratios than the p***enger car applications.All the applications of the 9 3/8 I have seen have been 31 spline." Here's more HAMB info on 9 3/8in. rear http://www.jalopyjournal.com/forum/showthread.php?t=109199
As mentioned, there are 28 and 31 spine. So the 3rd member will fit as long as it has the right spine count.
I got a 9" out of a 79 big Ford station Wagon, it had disc brakes, but it was called a 9 1/4". I put a new ring and pinion,3:50-1, no problem, I also narrowed it. and when I cut the housing I was surprised to find it was 3/8" thick.
One more thing. There are some with the fill hole in the carrier, and some with the fill in the housing. So it's possible the have two fill holes, one in the carrier, and one in the housing. It's also possible to have no fill hole at all.
There are also different length/size yokes - so swapping a "different" 9" might leave you SOL on the driveshaft. - Not a biggie, but you then have to swap yokes - which may lead to other interesting adventures.
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