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Discussion Starter #1
im swapping a 9-3/8 rear into my 67 galaxie.it had the smaller rear with the cover on the back before.the u joints are different sizes though.
is there a conversion u joint I can use?is this just a 1310 to a 1330 conversion u joint?
 

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I'll be interested to see how this goes because I'm planning to do the same thing in the spring.

I currently have the light duty WER axle in my '67 as you do and bought a 9-3/8" 31-spline out of a '68 Galaxie with a 390. I was told by the seller it was a 9" that's why I went for it but it turns out it's not. So I bought a 9" center chunk from another guy with the same 2.80 ratio that I currently have which came out of a T-Bird. Well that turned out to be a 9-3/8", too! That's the problem when dealing with people who aren't local.

From what I understand, parts aren't as readily available for the 9-3/8 as they would be for the 9". I think we're going to have to modify the length of the driveshaft, too.
 

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Discussion Starter #3
great ....I hope not.
my friend builds rears and had this center around.we also had a 9 inch full size housing with the correct brackets on it.i welded a steel plate in the upper control arm pocket to eliminate the cam washers.(we made adjustable control arms)
the center is the heaviest duty there is (weight wise too)its got a 3.0 gear and a 10 tab posi which he just rebuilt.
It doesn't look like you could use these axles with a 9 inch center because the center pin in the center section has a 1 inch pin and the 9 inch has a 3/4 pin.
one axle could be shortened to work but it looks like a new axle would need to be purchaced for the other side.
 

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I'll be interested to see how this goes because I'm planning to do the same thing in the spring.

I currently have the light duty WER axle in my '67 as you do and bought a 9-3/8" 31-spline out of a '68 Galaxie with a 390. I was told by the seller it was a 9" that's why I went for it but it turns out it's not. So I bought a 9" center chunk from another guy with the same 2.80 ratio that I currently have which came out of a T-Bird. Well that turned out to be a 9-3/8", too! That's the problem when dealing with people who aren't local.

From what I understand, parts aren't as readily available for the 9-3/8 as they would be for the 9". I think we're going to have to modify the length of the driveshaft, too.
Just FYI since I was on here a month ago with the same issue. Also wanted to swap out my 31-spline 9 3/8" for a 9" with same gears, there are none but you can get real close with 2:75 gears and 31 spline in a few vehicles mainly late 70's early 80's pickups. You can figure the correct ratio by counting the ring gear and pinion teeth and then dividing I believe it was the pinion teeth into the ring gear teeth count. Took a while but found a good complete 9" 2:75 rear diff, case, and axles on craigslist for $200.
Here is a link that lists most if not all Ford rear diff ratio's etc per year vehicle and model you can use for cross reference.
Ford Rear Axle Assembly Identification - Page 02 - FORDification.com
 

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I'm wondering now about the 9" housing I have spare.
How can I tell for certain it is not the 9-3/8 housing?
I have the WER diff in the car and bought the 9" just in case..........
Or is it a 9 inch ?
 

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I'm wondering now about the 9" housing I have spare.
How can I tell for certain it is not the 9-3/8 housing?
I have the WER diff in the car and bought the 9" just in case..........
Or is it a 9 inch ?
One way to tell if you have a 9 Inch is if you can't use a socket (have to use a wrench) on one or both (can't remember which) of the lower bolts when taking the pumpkin out, I can't remember if this is true also with the 9 3/8". Also the ribbing is slightly different on the 9 3/8" vs the 9" (see pic on link below). BTW I think the 9 3/8" is a good rear diff but ya just can't find parts for it and good luck getting an aftermarket posi like a true-trac or something in there although there were some limited slip 9 3/8" factory units produced. If need be post up a thread asking for help there are a lot of members who are well versed on 9" diff's like PSIG or Desertxl amoung several others.
Check this link out it helped me a lot.
Kevinstang's Ford Nine Inch Differential Page +
 

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Exact same thing here - I got the 9 3/8" (31 spline) on my '67 Gal now but had a Z code parts car (too far gone) that had a 9" (28 spline). Worked out perfect since it had all the proper spring perches and panhard mounts for the Galaxie. My plan is to rebuild that 9" with some goodies when the wallet allows.

Fortunately, both axles still had the tags on them so I was able to easily identify (below). Plan is to rebuild the 9" with a better (locking) gear, 31 spline axles & disk brakes and pop it in once ready. I'll keep the 9 3/8" axle with the 2.8 around just so I have the original.

Let us know how yours turns out.
 

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Discussion Starter #9
here is ours.the pinion support in a nine inch would fit right through the center hole in the 9 3/8.thats how big it is.
also look how many bolts there are on the pinion support.i think there are more on a 9 inch.
the cases are the same but the top of the center hole in the case needs to be notched so the ring gear will fit inside.also there is a little grinding that needs to be done on the inside back of the case to clear the ring gear too.
ours has the heaviest posi there was for the 9 3/8.its called a 10 tab posi.never mind the puny 8 3/4 mopar rear in the back.
 

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