# 3.23 10 bolt



## 1965goat (Sep 8, 2014)

is a 3.23 10 bolt high performance a good differential for a 65 gto? i have a 12 bolt posi now. is it better to stick with my 12 bolt or go to the 10 bolt 3.23?
:suspicious:


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## GTO JUDGE (May 14, 2005)

1965goat said:


> is a 3.23 10 bolt high performance a good differential for a 65 gto? i have a 12 bolt posi now. is it better to stick with my 12 bolt or go to the 10 bolt 3.23?
> :suspicious:


Depends on your application. The 3.23 is standard. The 12 bolt is heavy duty for more aggressive applications. You don't specify the gears in the 12 bolt. If you want a cruiser and increased mpg with the occasional stomp it feel then you may want to consider going that route. Depending on what gears are in there now, if you want to get on it often and highway driving is not typically where you drive it but rather shorter distances then the 12 bolt with 3.90's or so will suit you better. Many love the 12 bolt. It all boils down to what your driving habits are.

Someone had a 12 bolt 4.11 in mine. I wanted to put it back to Judge specs and sold the 12 bolt and purchased a new 10 bolt 3.55. I got the 10 bolt for pretty much an even swap. RPMS on highway went from 32 to 2800.

If you choose to go the 10 bolt route and the gearing is different, you'll also need to change your speedo gears or your odometer mileage calculator and mph will be off.


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## 1965goat (Sep 8, 2014)

awesome thanks! is there any way i can identify the gears in my 12 bolt now? any markings on the casing or anything? also, is it somewhat easy to install a new differential, and can i use lockers on mine if i keep it?


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## GTO JUDGE (May 14, 2005)

1965goat said:


> awesome thanks! is there any way i can identify the gears in my 12 bolt now? any markings on the casing or anything? also, is it somewhat easy to install a new differential, and can i use lockers on mine if i keep it?


Without taking the cover off you can do old school. Jack wheel off the ground. point your valve stem on a mark on the floor. Have someone turn that wheel one revolution as you watch your yoke/drive shaft and count how many times the drive shaft turns to the one revolution of the wheel. If it turns just over 4 times it will indicate in the 4. range.. almost 4 times it will indicate in the 3.90 range. If you remove the cover there should be stampings on the gears on number on one gear one on another add them. Mine added to 411 and the drive shaft turned 4 and 1/4 turns.

Not that hard to remove and install. Not familiar with lockers perhaps someone else can help you there.


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## WildTom65 (Apr 21, 2014)

*sell it to me*

I currently have a 4:10 ten bolt rear with no problems, but I'm looking for a 12 bolt to fit in my 65. If your thinking of selling the 12 bolt, send me a note.


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## 666bbl (Apr 13, 2014)

I raced with a guy that ran a 725HP BBC Nova bracket racer. It had a 5000 stall and a trans brake and ran low 10s to high 9s. It had one of the heavier duty GM 10 bolts back there. With 10X28 slicks and the chip at 4500 the car left every pass with the front wheels hanging nearly 2' for the 1st 40-50'. He'd get a season and a 1/2 out of a set of gears and ran lots of rounds. There's some thoughts out there that the "right" 10 bolt can be just as strong as a 12. A 12 uses 5/16 ring gear bolts, a 10 uses 3/8. Some 10s even have parts like seals and bearings that interchange with another tough rear axle, the 8.8 Ford. Just some random thoughts...


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