# 1970 GTO 12 bolt rear end



## HelpDeskGuy (Sep 4, 2008)

Hey all,

I ran across this guy who had a 12 bolt posi he couldn't ID so I had a look. The numbers/letters on the tube were LE 0619K and casting 3969278 I believe. After a bunch of searching I think this is from a 1970 GTO. Then I read on some other sites and they say that 12 bolt posi units were only available in the "Judge" option. I pulled the cover and it has a three series unit and someoen has but 4:88 gears in it with an adapter plate. My question is is this rearend from a 1970 GTO or is it from a Judge or am I way off?

Any help would really be appreciated. I was thinking of pulling the 10 bolt from under my 72 LeMans and putting it in there but if it is a true "Judge" only 12 bolt then I will probably sell it or trade it off.


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## ponchonorm (Jun 23, 2009)

I believe the 12 bolt rears came in the 455 equipped 70 GTO's. I'm sure someone will be along to confirm or deny.


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## HelpDeskGuy (Sep 4, 2008)

*Yes*

Thanks Ponchonorm.


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## 68greengoat (Sep 15, 2005)

I tried googling the casting number and kept coming up with a '70 - '72 Chevelle. See if you can find a date code on the pumpkin next to the cover. Should read something like D210. The last digit being the year...

Went to this site:

http://www.wallaceracing.com/axledata2.htm

Your LE 0619K could = LE - '70 2.73 GTO/GP, 06 - June, 19 - 19th, K - GM of Canada, non posi(since there isn't another letter). 

Although, there were no 2.73 diffs in a GTO for '70. And you shouldn't find a 2.73 in a 12 bolt anyway...


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## 05GTO (Oct 6, 2004)

ponchonorm said:


> I believe the 12 bolt rears came in the 455 equipped 70 GTO's. I'm sure someone will be along to confirm or deny.


:agree

Only offered on the GTO with a 455 HO for 1970

3.31 ratio WU open carrier XU posi, (C-TYPE AXLE) 12 BOLT 

3.55 ratio WV open carrier XV Posi, (C-TYPE AXLE) 12 BOLT


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## HelpDeskGuy (Sep 4, 2008)

Yes that was what I found as well on the LE. The casting number could have been 3869278...I'll have to look again when I get it here. It has a three series eaton unit in it. Someone has replaced the gears with 4:88 and used a spacer plate. Looks like someone media blasted it and painted it. Code on the tube was easy to find and read. The date code was 1970...I don't remember what it was exactly. Back then could someone have ordered this at the dealer and had put it in their GTO even if it wasn't a 455HO? And the K indicates it was a Canadian built unit correct?


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## 68greengoat (Sep 15, 2005)

HelpDeskGuy said:


> Yes that was what I found as well on the LE. The casting number could have been 3869278...I'll have to look again when I get it here. It has a three series eaton unit in it. Someone has replaced the gears with 4:88 and used a spacer plate. Looks like someone media blasted it and painted it. Code on the tube was easy to find and read. The date code was 1970...I don't remember what it was exactly. Back then could someone have ordered this at the dealer and had put it in their GTO even if it wasn't a 455HO? And the K indicates it was a Canadian built unit correct?


From Wallaces site, K was supposed to be Canadian. On the back of the axle tube, drivers side, see if you can find a 2 letter code like '05 posted. Should begin with a W or X..... That will tell what gears were in it originally.... The X codes are posi.....


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## HelpDeskGuy (Sep 4, 2008)

Ok Outstanding. I will have a look when it gets here.

There is no way to actually tell if it was from a GTO or not right? I mean it can be correct for a GTO but also be correct for a GP right? Thanks for all the help.


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## 68greengoat (Sep 15, 2005)

I'll let '05 field that one. I'm not sure........


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## HelpDeskGuy (Sep 4, 2008)

I cannot find the W or X code at all. Is there I should be looking in particular? The other numbers were very easily read.

Any help would be appreciated.


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## 05GTO (Oct 6, 2004)

The letter codes will be stamped (not cast) on the axle tube, if by GP you are referring to a Gran Prix that would not be the case. A-body and b-body rear ends were not interchangeable, more than likely the rear end is from a chevelle.

Here is a picture of a type-c chevy 12 bolt diff cover that was used on chevelles and was an option for the 70 GTO 455HO. I can't say that a "coppa" type order program was not available on the GTO. The PHS report will specify the correct rear end.


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## HelpDeskGuy (Sep 4, 2008)

Yes it has the cover. I am a long time chevy guy. I bought the 12 bolt thinking it was a chevelle rear end but then when I get the stamped numbers it says it was a 1970 GTO/GP rearend. I just assumed the GP was grand Prix. I am sanding the tubes now looking for the 2 letter code. I couldn't find the "LE" on any chevelle only GTO. I know the gears have been changed as it is a 3 series carrier with a spacer and 4:88 gears. I am just so confused. I don't want to slam this 12 bolt under my lemans and it be correct for a GTO where I could sell it and buy another 12 bolt and have money left to get the rest of the Endura parts I need for the front end of my Lemans. . . You know what I mean?


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## goat guy (Feb 28, 2010)

I just look under my 1970 gto and has 12 bolt with posi and XH with casting #9788202


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## GTO JUDGE (May 14, 2005)

Mine does too. 4:10 Gears. Plan is to replace with 3.55's next off season.:cheers


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