# 10 Bolt Versus 12 Bolt Rear Axle



## take5 (Aug 9, 2009)

What is the difference between a 10 Bolt & 12 Bolt rear axle?
I have a 1966 GTO with 10 Bolt rear axle cover.
Did '66 GTO's have 12 Bolt rear axle?

All information & input is welcome.
Thanks


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## 05GTO (Oct 6, 2004)

Only in 1970 the Chevy 12 bolt was optioned on the Pontiac A-body, then only with a 455HO engine.


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## take5 (Aug 9, 2009)

Thanks Randy,
I've always wondered when I've heard about 10 or 12 bolt rear end installations.


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## geeteeohguy (Feb 2, 2008)

The 12 bolt is a stronger axle, but the 10 bolt does just fine. They hold up amazingly well after over 4 decades of abuse!!


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## harp (Jun 22, 2009)

i spent 1000$ in the mid 70's on my 10 bolt in my 69 lemans, different setup's 2.56,, 4.56 posi, and the last time it crapped out i just went to a chevy 12 bolt, 3.56 posi, end of problems period!!! if you've got bigs in horseopwer, replace the ten bolt if matching #s isn't important.


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## Eric Animal (Oct 28, 2007)

I've managed to blow up a 10 bolt w/ 3.55's AND a 12bolt w/4.10's...both in 66 GTOs...years ago. If it's buildable, I can break it.arty: Seriously,they are both good rears. If you are gonna hae a lot of HP/TQ, go with the 12 bolt. The 10 bolt is fine and OEM for stock. If you are going to set a rear up, take your time and figure out what gear ratio to use for the kind of driving you will be doing,and the engine/trans you have......E


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## Chris Holabaugh (Jan 18, 2009)

If your going to have alot of horsepower it would be time to go with a Ford Nine inch.


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## plmberkevin (Aug 16, 2009)

Becarefull there are olds 12 bolts out there also stay away from them.If your making H.P


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## HoJo GTO (Sep 21, 2009)

*12 bolt is 30% stronger*

I picked up a 12 bolt housing and plan to build it with a posi and all new guts. I've heard a chevy 12 bolt is 30% stronger than a 10 bolt.


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## Too Many Projects (Nov 15, 2008)

HoJo GTO said:


> I picked up a 12 bolt housing and plan to build it with a posi and all new guts. I've heard a chevy 12 bolt is 30% stronger than a 10 bolt.


Yes, it is but as has been said, it isn't necessary for "normal" driving and stock engines. If you have, or plan to build, a high torque engine and abuse it regularly, then the 12 bolt may be necessary. Hopefully the axle you got is from a 68 and up Chevelle as Pontiac went to the wider axle in 67 but Chevrolet didn't until 68. There are compatibility issues with the narrower axle in a wide track body.


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## HoJo GTO (Sep 21, 2009)

I made sure to take very careful measurements of my 10 bolt rear before buying the 12 bolt. They are exactly the same width.

Most guys I know that have broken their rears have done so with slicks on their cars. :willy:


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