Differential case question

[Kyle Zevena]

Looking at a used carrier assembly (non-posi) and am interested in what it would take to "upgrade" it to a posi unit...

Are posi and non-posi carrierir cases different? can the clutch pack and hardware be added to a non-posi case? or would a new case and pack be required to chage a non-posi carrier to a posi carrier?

Thanks.

[William C.]

Re: Differential case question

The "carrier" that is the system that the ring gear is bolted onto is totally diffreent in design from posi to non-posi rear ends. The housing that the carrier inserts into is the same (where the pinion gear is held) but not the ring gear carrier, due to the requirement to configure space for the clutch pack.

[Mike E.]

Re: Differential case question

What vintage?
Putting a posi set-up into a non-posi housing is not a problem for 56-62 units--it's done all the time. Technically, the axles are different lengths, but again, doesn't seem to cause any issues at all. Carriers (to which the ring gear is bolted) are completely different for 56-62--a non-posi won't accept a clutch pack.

[Duke W.]

Re: Differential case question

Yes the cases are different. Original type Eaton Positraction cases are still available as far as I know. These are complete with the differential gears and clutch pack - ready to bolt on the ring gear and install in the carrier, and I think they are priced at around $450.

You can also buy a cone type limited slip case assembly from Auburn Gear, and they are less expensive. The cone type is cheaper to manufacture, but is considered "inferior" to the clutch back design, however, it should be adequate for street use.

If you buy an Auburn, just go for the standard preload springs unless you are seriously racing your car. Both types require the anti chatter additive in the oil.

Duke

[Duke W.]

My post, above, is specific to C2/3 63-79 *NM*

[Gary R.]

Re: My post, above, is specific to C2/3 63-79

As Duke pointed out the Eaton units are the better ones to use compared to the cone type. I'd like point out the new (made in Mexico) Eaton carriers come loaded with powdered metal spiders,HD springs and fiber clutches. They are poor choices for a vette with 300+ hp. The fiber clutches are one of the worse designs out, they were smudging in my hand on one job. The carrier housings are very good however and can be modified to give you better performance and life then a stock 4 spring setup.

If you look around for a good used 3 series posi carrier you'll find them about $250 bare. Add in for the best steel clutches and tune them and you'll have a great posi. You'll have to check the pattern and if you're going this far you might as well install new bearings/seals.

The Eaton posi carriers for the 65-70 vettes were not as good as the later carriers and the spiders were also better in the later cars.The later cars had poor clutches and many have broken without the driver knowing.

The best posi would be a custom built one with the best parts. If you're just looking for a posi and don't plan on pushing the car a stock unit would be ok, but it'll probably hammer- use 2 bottles of additive.
good luck with your project. I have a Blueprinted NOS 3 series if you need one. It is far from stock and has the best internals and NOS 10-17 spiders.