# What Posi gear ratio should I put in my rear end?



## Daisy II (Jun 20, 2020)

I have a Pontiac Tempest 1967 4 dr. I don't race the car, I drive it around to car shows and on the highway to work some times. I don't know what type of Posi to put into her. She has a 4 br carb, bore over 30 and rebuild engine and 2 speed automatic transmission. Any recommendation on a Posi and what brand to buy ??? 

Thank you for any advice you give to me!!
Daisy II


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## O52 (Jan 27, 2019)

Save your money. Unless you drive in the snow, race or other low traction situations, you don't need a Posi. 
With that being said, its not a bad idea to have the axle assembly looked at. If nothing else to replace the bearings.


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## Gremlin66 (Oct 11, 2009)

I went Auburn


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## LATECH (Jul 18, 2018)

Yukon LSD hands down good equitment.
And I have had good luck with yukon gearsets,
Ratio is what you asked about
You want more performance, put a turbo 350 in it, ditch the 2 speed
quicker and easier , and gives better performance


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## ylwgto (Oct 27, 2009)

my car was a one-legger with 2.73s for 20 years and I had tons-o-fun. just recently put in a built rear end with 3.25 posi expecting super-fun and I can barely burn out because my trans is so tired (from all that old fun). agree with LATECH, maybe upgrade your 2 speed for more fun first? 

or are you asking about gear ratio over posi vs. open?


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## Lemans guy (Oct 14, 2014)

Agree with LA Tech, I put a TH350 in mine to replace the Pontiac 2 speed,…

recommend having the trans set up for a dual gate shifter, then you have both auto and manual shifting. It bolts in without major modification.

Change the rear later if you prefer.


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## armyadarkness (Dec 7, 2020)

I think it's very subjective, but 336 is the pretty much the "united" suggestion around here for best ballpark ratio. As for the unit, I did an Auburn, cheap, and love it.

FYI: A posi will go sideways in the rain and snow, an open rear will not (within reason). It's a very grey area... but it's why so many 80's Mustang GT's are in the junkyard.

IMO, posi's are only a real benefit on a dry road, or dirt road, and only if you're struggling to get traction. Driving conditions and habits are what dictate your solution. Unless you drive like me and live in Jersey, my advice would be of limited use.









open to posi swap questions


Finished my engine refresh, now on to getting rid of the one legger! I have an open diff in my 8.2 10 bolt in my '66. Not sure what the gear ratio is. I'm going to do a 4 wheel disc conversion, so thinking i may as well upgrade to a posi carrier while the axles are out. a few questions: 1. is...




www.gtoforum.com


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## 67lemans (Oct 30, 2009)

(I assume you have a 326 still in the car?) I have a 67 lemans 2 door. Still got the 326 in it w small 4bbl.. Like others have said I put a turbo 350 in it (easy swap) made a big difference down low, no difference cruising. It had a 3.23 open and I put an Auburn posi in it and left the gears as is. It will easily do a two wheel burn out and catches a little chirp when it hits second, but I only have some 215/60/15s on it at the moment, so no big meats. I don't drive very far so the 3.23 does fine, I don't think I'd want anything higher, but thats getting into a lot of personal preference, others will differ. I have 3.08s in my trans am and I like that too, but it's lighter and has a 400 in it (same turbo 350).


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