# 1964 GTO Differential Question



## Al T (Mar 15, 2010)

I've got a 64 GTO convertible w/ 66 421 tri-power that this summer definately indicated it needed a posi rear 










I've got a line on a couple of 10 bolt posi carriers. Will these be a direct bolt in with me being able to use my existing axles? The seller states they are from a 64-66 GTO? Both are 3:23 ratio. One is rebuilt, the other is from a driver. Is there anything I need to ask regarding # splines, etc.

Thanks in advance.

Al T.


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## geeteeohguy (Feb 2, 2008)

Al, you should be fine. 3.23 is a great ratio for these cars. If unsure of setting up the gears (pinion), ask or get a pro to help. Good luck....


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## Al T (Mar 15, 2010)

geeteeohguy said:


> Al, you should be fine. 3.23 is a great ratio for these cars. If unsure of setting up the gears (pinion), ask or get a pro to help. Good luck....


Thanks for the reply. Supposedly the rebuilt carrier is ready to install. Anything I should check before I do that....... assuming I can make a deal.

Al T.


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## geeteeohguy (Feb 2, 2008)

The pinion depth will have to be set using a new crush sleeve in the housing. This is an exacting job best left to experts or someone with a manual and mechanical aptitude. Yes, the carrier bolts right in, but the pinion and yoke need to be set up properly for the correct ring-to-pinion gear backlash and contact.


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## BearGFR (Aug 25, 2008)

Al T. said:


> I've got a 64 GTO convertible w/ 66 421 tri-power that this summer definately indicated it needed a posi rear


Ah... the dreaded Ponho Pavement Python. Known to lie in wait, hidden in various roadside foliage and flora, only to ruthlessly strike the unsuspecting passing Pontiac, purloining significant amounts of tire tread....

There is no cure for its venom, only partial remedies of varying effectiveness.


Bear


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## geeteeohguy (Feb 2, 2008)

LOL!!! A 2" thick block of wood bolted to the floor under the accellerator pedal has been known to help.....


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## Instg8ter (Sep 28, 2010)

only difference will be dual lines instead of one....LOL. Theres a reason they used to say GTO stood for Gas, Tires & Oil. too bad they did'nt come from the factory with mini tubs for 14" wide tires. But then we would be blowing rear ends left and right, when it did hook up....gotta love torque in the low end...


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## 646904GTO (Feb 10, 2008)

Al T. said:


> I've got a 64 GTO convertible w/ 66 421 tri-power that this summer definately indicated it needed a posi rear
> 
> 
> 
> ...


It has been my experience that if you pull just the carrier, install the posi unit and put the unit back in with the original carrier shims on the same sides as they came out you will be just fine. Over the years I have done this successfully every time to the extent now when I do it I don't bother to check the backlash with a dial indicator like your supposed too. It always measures with in specifications. Also if you are going to replace the pinion you must pull the pinion bearing off and use the shims from under the original pinion. This will make the pinion depth correct. All the carriers and all the ring and pinion sets are exact to measure. The cases are the variable part, so using the original shims seems to work. I discovered this a long time ago when I used to build gear sets and ran out of the correct size shim packs and only had the stock stuff to use, and it worked so I started checking assemblies with the stock stuff and they always measured out correct, weird, huh.


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## 646904GTO (Feb 10, 2008)

3.23 are a perfect street gear with a 1to1 final drive


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