Non posi to posi - What is needed?

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Non posi to posi - What is needed?

Post by magisnyc » Fri Jan 05, 2007 11:30 pm

I have a non posi 12 bolt unit with what I believe are 2.73 gears. I want to keep the gears as I do alot of highway driving but I do want to switch to a posi carrier.

Can I just buy a posi carrier and swap it in? Do I have to change any other parts?

Car is a 71 Chevelle with a mild 350.

Any help would be appreciated.


open to posi switch out 12 bolt chevy

Post by monzaz » Tue Jan 09, 2007 1:41 pm

Ok ...

Open or Posi carrier in any GM differential will have the same carrier ratio breaks.

So Yes , If you want to keep the 2.73 gears you can remove the 2 series open carrier with ring gear. Remove the ring gear and install it onto the 2 series posi (limited slip) unit and reinstall. It will be very close BUT it is always best to double check the pattern and the backlash measurement to assure specs are correct.

On a used gear backlash can be with in .005-.010. If it is NOT with in these specs you should reshim the carrier with a shim kit from any speed shop or gm dealership. I do have all the parts you need even the 2 series posi if you would like a quote.

The 2 series 12 bolt units are NOT sold in the aftermarket...GM only I recondition these units.

If you really like to do it right now would be the time to replace all the rear diff bearings to new that would assure you would rpobably never have to open the rear up for a good long time again. 75.00 geat you all the bearings shims gaskets seals ring gear bolts nut crush sleeve etc. to do the complete job.

Hope this info helps. Good luck in the project. always here if you need more help. Jim

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