I am looking into fitting a posi lock differential to my 55 TBird and looking at the centre it doesn't seem to be like the other Dana diffs.I know it is not a 9" as the pinion support does not separate, yet it is a Banjo style?
I see the Dana diffs have a salsbury style housing?

So I would like some help identifying my diff.
Please pardon the grease but here is a picture of it.

No argument with Paul’s suggestion regarding moving to a ’57 or later rear axle assembly, CK.

I’m fuzzy on this, but my recollection is that there is SOMETHING about the ’57 station wagon and courier rear axle assembly that makes it the best choice for putting it under a 'Bird. Perhaps the location of the spring perches? Or, maybe it’s something to do with the brakes. I wish I was clear on this for you.

My recollection, also, is that the ’57 FoMoCo differential is NOT a true 9 inch. It is commonly referred to as a 9 inch, but to put an actual 9 inch into the ’57 housing, some grinding on the housing has to be done to get the pig in.

The spring perches or brakes on the ’58 and ’59 Ford wagons may be the same as the ’57… but I don’t know.

I wish I could remember where I read or heard what I’m trying to pass on to you here. I am sure about the installation of an actual 9 inch differential into a '57 housing. -I did it in '10 with a friend on a '57 'Bird. –My age is showing on the rest of it though.

Hope this helps. Maybe someone else can add to this.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

As far as I remember the sedans had the small bearings, the wagons and courier the large bearings. Not sure what the 57 Bird used but either would be ok for a street car..

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Ford 9in rear axels. googal ford 9in rear axels,the site has all the info you will ever need. they say 57-59 ranchero and 65-67 mustang hps ar the same width 57,25. giv it a try,ther ar other sources listed. cliff 57ranchero