6 bolt posi

[1964C10]

First thanks all for making this such a great site! I have found more answers here then anyyyywhere else, and some cool rides and ideas as well. On to my question, I did a lot of searching here but I am still confused. I have a 64 stock 12 bolt non-posi with 6 lugs. I am planning on keeping the 6 lug but have been thinking about upgrading to a posi, in order to do this, do I need to swap out my complete rear end or can I keep my axles, housing etc? Furthermore, I understand the benefit of positraction but I am planning on making this a daily driver with just a streetable ~350-400 hp fuel injected engine so is a posi really necessary? Thanks again all!!!

[shortbed70]

Well to anwser your last question no you really dont need one but it helps on bad weather days to have them sometiomes. You can keep everything except your carrier that your gear is attached to you need to count your splines on your axles (probably 30) then you can order a new carrier with springs and clutches to have your "posi". I also wouldn't try to set the stuff up yourself unless your very mechanicly inclined because if it isn't right its a time bomb. There are also 3 and 4 series carriers. You can get gears for both but the 4 has a better selection. Eaton,auburn,detriot are a few. Good luck!

[1964C10]

Thanks Shortbed!! I just spend two days, striping, sanding etc on my housing so I am glad to know it wasnt in vain for later I have been wanting to do it myself but how would you define mehanically inclined? I work on my 95 Mustang and my wife's z28 all the time, I am just curious why you say time bomb, I mean what can will go wrong?

[TR65]

Hey 64,

I put an Eaton in my 65 a year or so ago, works very well. If you want to put those 350-400 HP on the road then you need a posi. I was leaning towards the Auburn but my racing buddies said to go with the Eaton.

If your gears are good then you don't have to worry about setting the pinion position which is the hard part. All you have to do is shim the new carrier to the correct lash. It is a pain, you need a dial indicator and a bag of shims, and some patience. I wound up machining a shim to the correct thickness.

The posi carrier will have the spider gears in it. Should replace the carrier bearings and axle bearings while you are at it. Don't forget to add a bottle of friction modifier to the gear oil (makes the posi work right).

Good luck,

TR

[ruffrida2005]

HAHA short bed is correct, if you dont have it shimed correct to get the correct alignment for both the ring and pinion gear. You have to use dials on it so you dont have too much slack in it. I have never done one, but have read a lot about it. I also have the same truck and rear end as you. I have a 4.10 gear in mine, and if you want better highway gears you will have to swap to a 3 series carrier, and use atleast a 3.08 - 3.42 gear. Thats what I'm planing on doing. I have a 400hp motor with t350 in mine. and I just spin no matter what gear im in. Posi would get a good thing but I've heard it's not really good on fuel.

[shortbed70]

Well its been discused before about used gears and new units but I won't open that can of worms. All I can say is get the tolerences where they need to be because if not the pinion can and will contact the carrier and put ALOT of metal into your oil and we all know what metal does with bearings...Have you ever torn apart a rearend before? Do you have a magnetic dail caliper and know what your looking at? Good luck and if you run into problems thats what this site is great for is getting anwsers. Keep on truckin...

[1964C10]

Thanks guys for the insight, when I do the work I would definitely be changing out all the bearings just to be safe. It's not in the near future plan but at least now I know where I am going

ruffrida, I actually have 3.73 gears in mine which isn't too bad although gas mileage will suffer. Are you a reservist?

[Captainfab]

If your differential is an original '64 model it will have the 17 spline axles which there aren't any aftermarket posi's for. You will have to switch your axles for the '65 and newer axles which have 30 splines. As for setting up the differential, there are instructional videos/DVD's that show you how it's done.

[1964C10]

Shortbed70: Thanks for the info! I have never torn into a rearend before but I plan on learning all I can before I do and well that is part of learning right? doing it for the first time, and if it goes wrong it's only money hahahaha j/k. I do have the magnetic dial and I have used it before to check rotors which I thought were warped.

John: I will open the case again today and check on the spline count, either way, I am glad I can at least keep the housing becuase I really wanted to get one of those polished aluminum covers instead of having to strip/paint my old one.

[ruffrida2005]

I'm actived duty army. I'm glad that I looked at your post I didn't know that our rearends came with the 17 spline axle, I thought they had 30. Atleast that's what summit says!

[1964C10]

Be safe over there man! I am Navy reservist myself, going to Intelligence Specialist school at the moment, I am sure I will get activated as soon as I graduate next year (one weekend a month school).

I am going to count right now, just to make sure....

Originally Posted by ruffrida2005

I'm actived duty army. I'm glad that I looked at your post I didn't know that our rearends came with the 17 spline axle, I thought they had 30. Atleast that's what summit says!

[1964C10]

Well I am only able to see a portion of the axle but to my best estimates it would put it much closer to 17 then to 32 since I saw only about 5 splines which seemed about a quarter of the way around.

[ruffrida2005]

I actully just got back from deployment. 3rd tour. One weekend a month school must be hard. I dont see how yall do it, I would forget everything!

[1964C10]

Thanks for your service!! 3 tours wow! It is harder then I at first thought because we can't take any study materials home so we study and then test. For the rest it really isn't just a weekend a month anymore there are so many other things to do during the time off, GMT, staying in shape, paperwork, pay issues, uniforms etc, but it's always nice when we do go out and join the active fleet that they can't tell we are reservist because we stay up to speed

[ruffrida2005]

Well that's really good that yall stay up to speed. I cant say the same for a lot of Army reserve units. Some are really high speed. But what I think you should do with your axle and I'm doing the same is swap it out with a 65 to I think 69 rear in. I think in 70 they lengthend the rear in. would be more cost effective to go with one of those rear ends with a 3 bolt carrier, and go with a 3.08-3.42 gear.

[1964C10]

Do you know if the bolt pattern on the 12 bolt cover plate stays the same? I deciding on whether to paint me old one if I am going to swap rearends later anyways or to buy one of those polished aluminum ones, they are fairly pricey so I dont want to blow the money if I have to toss it later.

[shortbed70]

Chevy 12 bolts are the same cover.

[1964C10]

Thanks Shortbed70!

[ruffrida2005]

Can you just swap out the carriers in the housing from 4 to 3. I wouldn't mind keeping my same rear end but change everything out. I just dont want to buy a rear end that I know nothing about!