# Posi?



## LouCabra (Jul 20, 2015)

Hello,

finally starting on what I hope will be an easy rear end swap. Several months ago I picked up what is supposed to be a complete 3.55 rear end from a 67 GTO to replace my peg leg 2.56. After reading some post here I was expecting to see some kind of spring in the middle of the chunk, but it’s not there. Can anybody shed some light on whit I got?

TIA


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## armyadarkness (Dec 7, 2020)

I'm only a novice on identifying GTO diffs, although I have rebuilt several. That looks like an open diff to me


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## armyadarkness (Dec 7, 2020)

BTW, I put an Auburn diff in my existing open rear, and it took about 2.5 hours, on my back in a driveway.


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## Baaad65 (Aug 29, 2019)

Do the axels turn in opposite directions or can you spin one while the other one is locked?? Here's what my Chevy 12 bolt Eaton posi looks like.


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## Sanders Speed (Oct 23, 2020)

You have a heavy duty 4 pinion posi, the carrier is a two piece bolted together. Cone style posi clutches.


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## LouCabra (Jul 20, 2015)

Sanders Speed said:


> You have a heavy duty 4 pinion posi, the carrier is a two piece bolted together. Cone style posi clutches.


Thanks for the info! I googled "Cone type posi clutches" and it took me to an AuburnGear web site The diagram looks similar to what I have, but not exactly. Can you (or anyone else) confirm who made the differential? I like the idea "of a heavy duty posi". By the way, the reared is currently on some stands. If I rotate one of the axels the other one turns in the same direction. Also, if I rotate the yoke both axels turn in the same direction. Hope this helps me identify what I have.

Thank you all.


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## 1969GPSJ (Feb 26, 2020)

Lou 
I have the exact rear carrier definitely a posi, the ring gear should have numbers stamped on it to confirm the gear seat , mine is 42-13 which =3:23 rear gear ratio to confimr you have a 3:55 divide the larger # into the smaller # 
remember to add friction modifier for posi + rear gear fluid I think the heavy duty is 3 pints


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## LouCabra (Jul 20, 2015)

1969GPSJ said:


> Lou
> I have the exact rear carrier definitely a posi, the ring gear should have numbers stamped on it to confirm the gear seat , mine is 42-13 which =3:23 rear gear ratio to confimr you have a 3:55 divide the larger # into the smaller #
> remember to add friction modifier for posi + rear gear fluid I think the heavy duty is 3 pints


Great to hear. Do you know what brand yours is? Don’t know if you have to wort about different brands fitting, but if I want to go the 3:23 route rather than 3:55 it might be helpful. As everyone can tell I don’t know jack about differentials, but I’m waiting on a book from Ames so hopefully I’ll understand more soon.


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## 1969GPSJ (Feb 26, 2020)

Lou 
1969 Pontiac rear with casting number on the axle housing 9795082 on the right side near the cover (like 5 o'clock position)
I am not sure which carrier you have so I can speak to the interchangeability for the 3:23 gear set 
sorry I already sealed mine up so I cant get you a picture


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