I want to change my stock 12 bolt to a posi. I'm going with the Eaton unit and keeping my current gearing which is 3:31. Can I just install the posi and put the axle shims back the same way they were? I won't be changing the ring and pinion so I don't need to do anything there do I?
Thanks, Jody

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jodysss396 (or Jody)
1969 Chevelle SS396
Fathom Green
Numbers Matching
TC member #921
A.C.E.S. #4348
Jody's 69 SS396 (http://chevelles.com/showroom/MVC-015S.JPG)

Installing a different carrier, but using the same gears may or may not allow you to use the same shims. The pinion depth should be fine, but it is conceivable that Eaton made its new posi carrier a little different than the one that is already in your car which would cause you to need a different shim stack. Start out with the original shims and check your backlash and engagement pattern and go from there. That should get you close, but you might have to make some adjustments to make it perfect.

Maybe Biggearhead will chime in here. He knows alot more about setting up rear ends than I do.

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69 Camaro
400 Small Block
Trick Flow Heads
Comp 282S solid cam
Performer RPM intake
750 CFM Holley
and a Muncie four speed
Pics of My Car (http://cards.webshots.com/cp-25368180-AyNI-album/38182394akfhbj)

Because of machining tolerances, most of the time you need to make small adjustments in the shim thickness to get the backlash and bearing preload correct. I suggest getting the super shim set (for the differential only) and new Timken bearings with the Eaton posi so you will have everything you need when you do the job. Be sure you check the backlash BEFORE you remove your standard differential so you will know what to set it at with the new posi.

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'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drivetrain Parts & Service
www.lubedealer.com/biggearhead (http://www.lubedealer.com/biggearhead)

[This message has been edited by big gear head (edited 01-29-2003).]

Thanks for the help guys. Looks like a fairly easy job but as I go I may have more questions. I will surely get new bearings and a shim kit before I start.
Jody

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jodysss396 (or Jody)
1969 Chevelle SS396
Fathom Green
Numbers Matching
TC member #921
A.C.E.S. #4348
Jody's 69 SS396 (http://chevelles.com/showroom/MVC-015S.JPG)