# 1964 12 bolt to 10 bolt



## remy30006 (Jul 7, 2013)

I'm in the process of buying a 64 GTO but it has a 12 bolt posi with 4:10 gears. I'm assuming it should have a 10 bolt? I want to get it back to original.


----------



## geeteeohguy (Feb 2, 2008)

You assume correctly. It takes an 8.2" 10 bolt, and the '64 is a one year only rear end, with smaller diameter upper swing arm bushings. Any 8.2 rear end '64-'72 from an A body will fit, but since you want it original, you need to locate an original '64 unit. They come in all ratios, so, depending on what transmission is in the car, and what type of driving you do, you'll need one with the right gear to suit your needs.


----------



## MotoNut (Dec 5, 2011)

I would like to have that 12 bolt with 4:10 gears for my 65 tempest.


----------



## ALKYGTO (Mar 29, 2010)

I have a 64 Tempest 10 bolt 3.08 open.

Edit: Alky, you know better.... 

68'






Can't really blame a guy Greeny......


----------



## zman123 (Aug 2, 2013)

*64 GTO 12/10 bolt rear?*

took my 64 convertable in to get the rear gears changed and was told that it is "an extremely rare" rear end. 12 bolt housing with 10 bolt gears. Is this possible? If so how many were produced this way and why? If there is a 64 expert out there that knows the answers I'd be grateful.


----------



## geeteeohguy (Feb 2, 2008)

All '64's came with an 8.2 ten bolt gray iron rear end. No exceptions. Your '12 bolt' may be a Chevy, Olds, Buick, or who knows what. Casting numbers and date codes will tell you, but you need to put in the work. Whatever it is, it isn't original to the car. Good luck.


----------



## BearGFR (Aug 25, 2008)

zman123 said:


> took my 64 convertable in to get the rear gears changed and was told that it is "an extremely rare" rear end. 12 bolt housing with 10 bolt gears. Is this possible? If so how many were produced this way and why? If there is a 64 expert out there that knows the answers I'd be grateful.


If it's what I think it is, it's neither rare nor desirable. It's a "type-O" rear axle that was most often found in Oldmobiles. The rear cover has 12-bolts, but inside it has 10 bolts on the ring gear. These axles aren't as strong as even the original 10-bolt was. Google is your friend. A few searches should find you photos of that they look like from the outside.

Bear


----------



## HaloPlayer (Jun 22, 2013)

My '64 Lemans was a factory 6. Think the factory 10-bolt rear end will hold up to a mildly built 400 ?


----------



## ALKYGTO (Mar 29, 2010)

With an automatic and street tires it should last no problem. Change the fluid though, it could be 50 years old! :lol:


----------



## OhioLS2 (Jun 10, 2013)

ALKYGTO said:


> With an automatic and street tires it should last no problem. Change the fluid though, it could be 50 years old! :lol:




yes! being done to our 67' le mans as we speak


----------



## HaloPlayer (Jun 22, 2013)

ALKYGTO said:


> With an automatic.....


Not exactly what I was planning. I'm thinking an M-20 or 21 4-speed. Does that mean I should change the internals or will I be forced to upgrade the entire rear end?


----------

