[tallrandyb]

I want to convert my 3.55 open rear to the correct (original) 3.23 rear gears (original manual + A/C car) and would like to make it a posi (officially Safe-T-Track but I just use posi as general term) while I'm in there. So far I have found plenty of diffs for up to 3.23 and then the 3.36's and higher, but I'm striking out finding just a set of the 3.23 gears. Am I looking in the wrong places?

Shop manual says one diff for 2.73-3.08 and another for 3.23-4.11, but all current diffs I see online cut over at 3.36?

Any help appreciated! I'd like to get my rpms down some since I'm running the correct Muncie M20 trans. Thanks!

[62 bv]

i got one for sale out of my 64 gto let me know if you need picks

[tallrandyb]

sounds great if you want to post/send some pix. I assume you have the full diff+ring+pinion that I can drop in, I'd just need new bearing sets?

Did the posi hold well? tire marks pics?

[Kenth]

3 different cases, one 2.56-2.73, one 2.93-3.23 and one 3.36-4.33.
Also 3 different styles, one 1964-65 6 bolts holding case halves, one 1966-69 8 bolts holding case halves and one 1970-72 8 bolts holding halves and left-handed bolts holding ring gear.

[62 bv]

hi just 323 ring and pinion and carrier

[geeteeohguy]

Originally Posted by Kenth

3 different cases, one 2.56-2.73, one 2.93-3.23 and one 3.36-4.33.
Also 3 different styles, one 1964-65 6 bolts holding case halves, one 1966-69 8 bolts holding case halves and one 1970-72 8 bolts holding halves and left-handed bolts holding ring gear.

This^^^^^. Don't know why people keep saying that the gears are interchangeable between different series carriers.

Most replacement gears are 3.55 and steeper.....I haven't run a gear that steep in over 30 years and never will, because my cars are used on the street. Understand the OP wanting to drop his cruise rpms..... a 3.23 is just about perfect as a compromise gear between performance and touring with no overdrive.

[tallrandyb]

Originally Posted by geeteeohguy

This^^^^^. Don't know why people keep saying that the gears are interchangeable between different series carriers.

Most replacement gears are 3.55 and steeper.....I haven't run a gear that steep in over 30 years and never will, because my cars are used on the street. Understand the OP wanting to drop his cruise rpms..... a 3.23 is just about perfect as a compromise gear between performance and touring with no overdrive.

So if I have a 3.23 ring and pinion pulled from a 64 going in my 65 GTO, can I use this posi and this install kit:

https://www.ronsmachiningservice.net...-3-23-5420114/

https://www.summitracing.com/parts/yga-14085

This shouldn’t be this hard to get my rpms down. I had my years of fun with a 4.11 chevelle 12-bolt we swapped in, but even my 3.55’s now have it wound up too high for my liking at 80 on the highway.

Thanks!


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[62 bv]

that will work

[Bill Hanlon]

Changing from a 3.55 to a 3.23 gear isn't going to do much to your 80 MPH RPM.
Assuming 27" diameter tires, your 3.55 rear gear will have your engine turning about 3525 RPM.
A 3.23 would slow it down to just over 3200 RPM. Seems like a lot of work for a 10% reduction in engine speed.

[tallrandyb]

Originally Posted by Bill Hanlon

Changing from a 3.55 to a 3.23 gear isn't going to do much to your 80 MPH RPM.
Assuming 27" diameter tires, your 3.55 rear gear will have your engine turning about 3525 RPM.
A 3.23 would slow it down to just over 3200 RPM. Seems like a lot of work for a 10% reduction in engine speed.

Agreed not a big change but I'll get a posi at the same time and a more usable first gear, plus will make it correct for my car with A/C. So 4 improvements at one time!

[geeteeohguy]

Originally Posted by Bill Hanlon

Changing from a 3.55 to a 3.23 gear isn't going to do much to your 80 MPH RPM.
Assuming 27" diameter tires, your 3.55 rear gear will have your engine turning about 3525 RPM.
A 3.23 would slow it down to just over 3200 RPM. Seems like a lot of work for a 10% reduction in engine speed.

I went from a 3.55 to a 3.36 in my '65 GTO and was impressed with the improvement on the highway. Cruise speed went up 10 mph. Seems small on paper, but driving the car is much more pleasant. Have had several first-gen GTO's with the 3.23 ratio and stickshift, and they do MUCH better on the highway than the 3.55 cars. Again, on paper it doesn't seem worth the bother, but in actuality, a huge improvement and worth the effort.

[tallrandyb]

Thanks to 62 bv for the 3.23 ring and pinion set. rebuild kit purchased from Summit and 2.93-3.23 range posi purchased from Ron's Machining Service. Now I just need to find a reputable installer in the Orlando area.

[62 bv]

how far are you from sarasota i have a friend there owes salt works he can do it for you ask for tom tell him brody sent you

[tallrandyb]

Thanks Brody, that is about 3 hours from me so would be a long haul to wait or drop off. I'm in the Orlando/Winter Park central Florida area.