# 1966 differential ID



## Tri-Power (Jan 10, 2008)

Ok, i have searched through old threads on here for quite a while tonight but i couldn't find the one i seem to have pictured in my mind were somebody linked to some different pictures showing the differences in axle assemblies.

I am positive that what I am working with is a BOP 10 bolt. My problem is I would prefer to have a matching differential if the current one is not. My car is an original auto-2spd with the original tri-power, and had factory Air. From what i've seen this means that I would have a 3.23:1 rear gear set. (I would keep this ratio)

I know for a fact that it is currently an open carrier, but I cannot find the code to say exactly what the axle expects (I know it should be WF) . I know precisely were the 2 letter code should be on the RH axle tube, and it is not there. I also have heard there was a stamping break down which resulted in the 2 letter code being moved to the top of the LH housing? were on the top LH side should it be? I cannot find the 2 letter code anywere. I do have easy access to two codes though:








It seems to read....
top tag: 1735
bottom casting: 9783393
^^Can anyone decode that???^^

I plan on replacing the current carrier with a limited slip unit. Would people recommend auburn? or eaton? or what? does randy's have good prices? I know most people recommend Randy's.

I'm a little lost here guys, and i guess I'll just reuse the current housing if I cannot prove it's non-original. Any info on how to identify these rear axle assemblies would be greatly appreciated, because there is no guarentee what this axle is out of. (If it's not the original)

I can look at alot of different parts that might be identifiers as well because i have it all apart let me know what to look at if there is anything else that would tell me what it is.


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## 05GTO (Oct 6, 2004)

Ok, i have searched through old threads on here for quite a while tonight but i couldn't find the one i seem to have pictured in my mind were somebody linked to some different pictures showing the differences in axle assemblies.

Here is a picture showing the differences in BOP and C rear ends.









This is the cover on Pontiac








I am positive that what I am working with is a BOP 10 bolt. My problem is I would prefer to have a matching differential if the current one is not. My car is an original auto-2spd with the original tri-power, and had factory Air. From what i've seen this means that I would have a 3.23:1 rear gear set. (I would keep this ratio)

I know for a fact that it is currently an open carrier, but I cannot find the code to say exactly what the axle expects (I know it should be WF) . I know precisely were the 2 letter code should be on the RH axle tube, and it is not there. I also have heard there was a stamping break down which resulted in the 2 letter code being moved to the top of the LH housing? were on the top LH side should it be? I cannot find the 2 letter code anywere. I do have easy access to two codes though:
My 66 does not have the stamp either, I've had the rear out and and cleaned it before painting and there is no code stamped anywhere on either tube. My casting number and date codes match and my rear is also an open 3:23









It seems to read....
top tag: 1735 This date code may be I135 which would be Sept. 13, 1965, check the date code on your data plate
bottom casting: 9783393 this is the correct casting # for 66
^^Can anyone decode that???^^

I plan on replacing the current carrier with a limited slip unit. Would people recommend auburn? or eaton? or what? does randy's have good prices? I know most people recommend Randy's.

I used Randy's for the ring, pinion and carrier replacement on my 67 12 bolt type C diff, good guy to deal with

I'm a little lost here guys, and i guess I'll just reuse the current housing if I cannot prove it's non-original. Any info on how to identify these rear axle assemblies would be greatly appreciated, because there is no guarentee what this axle is out of. (If it's not the original){color=red]Not being stamped and the casting number pretty much confirm it is probably a 66 because of the stamping machine breakdown,[/color]

I can look at alot of different parts that might be identifiers as well because i have it all apart let me know what to look at if there is anything else that would tell me what it is.


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## Tri-Power (Jan 10, 2008)

arty:Thanks Randy!arty:


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## MaL (Jun 12, 2008)

I too am having this issue.

I have a '66 coupe, 4-speed, no AC, standard diff.

There's no code stamped on the tubes where they should be.
But here are the two from the carrier. I'm seeing E257 and then 978389 (is this missing a digit?) If the date is right, is this a '67 rear on my '66?

What do y'all think?




Edit:

LH rear drum info- does this help ID the rear?
I read-
KH E237 74439
(again, a '67 stamp?)


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## 68greengoat (Sep 15, 2005)

I know for a fact that it is currently an open carrier, but I cannot find the code to say exactly what the axle expects (I know it should be WF) . I know precisely were the 2 letter code should be on the RH axle tube, and it is not there. I also have heard there was a stamping break down which resulted in the 2 letter code being moved to the top of the LH housing? were on the top LH side should it be? I cannot find the 2 letter code anywere. I do have easy access to two codes though:

The information I have sez "In some instances the axle code was stamped on the drivers side axle tube in '66". However, it doesn't state whether it is located on the front or rear of the axle.
If it's a '65, which your date code indicates, it still should be stamped on the back passenger side of the axle tube. For an open 3.23 the code would be XF in '65. I wonder if they used same casting numbers for multiple years like they did on some engine blocks?


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## 68greengoat (Sep 15, 2005)

MaL said:


> I too am having this issue.
> 
> I have a '66 coupe, 4-speed, no AC, standard diff.
> 
> ...



Your date code looks like it's the 25th day of '67. Can't make out the first letter. Almost looks like a 3 or 8, maybe a "B"? The 2 letter axle code should be on the back of the passenger side tube. There was a sticker on the left rear brake drum with the same 2 letter code. It looks like you are missing a digit in the casting number. Unless it's a non BOP. Maybe non BOP's only had 6 digits? Even my '71 diff. has 7 digits. I would guess Randy could verify.


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## 68greengoat (Sep 15, 2005)

Edit:

LH rear drum info- does this help ID the rear?
I read-
KH E237 74439
(again, a '67 stamp?)

[/QUOTE]

KH isn't a valid axle code. Looks like the diff. is definitely a '67.


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## Too Many Projects (Nov 15, 2008)

Axle E257...E=May, 25th, 1967 casting date.

Drum May 23rd, 1967

I need that rear for my 06A 67 car....


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## Tri-Power (Jan 10, 2008)

68greengoat said:


> If it's a '65, which your date code indicates, it still should be stamped on the back passenger side of the axle tube. For an open 3.23 the code would be XF in '65. I wonder if they used same casting numbers for multiple years like they did on some engine blocks?


My car was built in '65 but Is a '66 a very early '66.


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## MaL (Jun 12, 2008)

68greengoat said:


> ...It looks like you are missing a digit in the casting number. Unless it's a non BOP. Maybe non BOP's only had 6 digits? Even my '71 diff. has 7 digits. I would guess Randy could verify.


I've had no luck in finding out about the 6 versus 7 digit casting numbers. Thanks for the help so far though


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