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Identifying Differential
8" and 9" rear ends prior to 1968 had the filler in the rear of the housing. 8" were more of an oval shape, these two factors are why we're all saying it looks like an early 8".

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
(01-19-2020, 09:22 AM)jpaz Wrote: I thought it looked like the 9” from a 63 Galaxy, like the one shown in the link? They show a 9” with a drain plug and two dimples on either side. Maybe I was looking at the wrong picture? Anyway hopefully you can figure it out. Good luck.
+1 if you also look at the poster’s pic his axels appear to taper at the ends indicating an early 9”.

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason

[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
Don't ya just love it when someone decides to put whatever they can find in a classic car? 
I would have thought that IF the PO decided to transplant a 429/460 with (presumably) it's matching C6 trans, he would also have installed the rear axle out of the same vehicle, unless it was from a truck. The car was an H code, so it would have had the 9" I think. That would have been better to leave in if it was not broken.
The original poster needs to offer more info. Does the car still have the original door data sticker? What axle does it list? He still did not say what car he has unless I missed it without rereading.

 I learn something new every day!
If the OP can put a deepwell socket on the bottom two nuts for the center section, it's an 8". If not, it's a 9".

[Image: wy1.jpg]

[+] 1 user Likes Hemikiller's post
Thanks for more info.

For those asking its a 1971 Mach 1, didn't really think it would matter what the car was since I gave the original Engine, Transmission and Differential codes from the factory listed next to the VIN that I looked up with this handy link https://www.7173mustangs.com/misc.php?page=1971

Having looked at the 63 Ford Galaxy differential I am starting to think that might be the diff that was installed on my 71. I have no idea why they would choose that, but I guess it was what was available at the time. Its not like I bought this thing fully restored. It was running and in decent condition internally and externally.

I will continue to research the Galaxy line of ford diffs to see if I can track it down. Hopefully I will have time to see if there is a stamp present that will identify it.
While you're under there looking for a tag, look at the bottom front at the locations Hemikiller pointed out, that's a sure indication of if it's a 9" or not.

A '63 Galaxie would be a strong possibility, as it has the same width axle as '71 to '73 Mustangs.

The axle code just indicates the ratio and whether it's a traction axle, not what type or size, for many years and models of Ford cars.

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
One more question, do you yet know what the ratio is? Also, is it a tration-lok type or open?
I know, more questions!

 I learn something new every day!
He said earlier that it came with a code 6 axle, 3.00:1 open.

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
Came with a code 6, but who knows whats in it. Fingers crossed that the stamp is still with it somewhere. Um, when I had it on stands the other day if I moved one wheel the other would turn too, but then it stopped after a little while and just the 1 wheel would turn.
So that means it has an open differential. If it was a posi then both wheels would spin, but one would spin in the opposite direction of the other.

run_horse Run Horse Run!
John 72 Q Code
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