# Ring gear size.



## pontiacsforeverred (8 mo ago)

Hi guys I have a original 3.90 gear ratio, would like to change to a 3.23 what size ring gear and pinion do I need on a 66GTO


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## armyadarkness (Dec 7, 2020)

If it's the factory differential, then just get an 8.2" BOP ring and pinion set. Youll likely need to get a 336. Dont see 3.23 anywhere


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## O52 (Jan 27, 2019)

IIRC the 3:23s require a different carrier.


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## Scott06 (May 6, 2020)

O52 said:


> IIRC the 3:23s require a different carrier.


Correct 3.23 and down is one differential , 3.36 and up is another 






Gear & Install Packages - Buick Olds Pontiac Car - GM 8.2" BOP - Ron's Machining Service







www.ronsmachiningservice.net





these guys carry a lot for the 8.2 BOP.


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## geeteeohguy (Feb 2, 2008)

Yep. With your 3.90 gearset, using your parts, you can only go as low as a 3.36 ring and pinion. I converted the 3.55 rear in my '65 GTO to a 3.36, and with 29" rear tires, it pencil's out to 3.23. Stock tires are 26.5". So not all is lost. Just changing the 3.90 to a 3.36 will help immensely with the driving characteristics of the car. Cooler engine, better mileage, lower noise and rpm, longer engine life, higher cruise speed. While 3.90 gears are badass and are bragging material, they are not needed with all the torque Pontiacs produce.


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