I thought I knew this... but age is making me question my own knowledge... I searched for the answer, maybe there somewhere... I just need confirmation on whether all 12 Bolt 68-72 housings could be upgraded to a Positraction unit... Or is there something about the Original Factory Posi Housing that is unique? I am looking at a complete peg leg 12 Bolt for 300...

Thanks,
Rich

Yes all can be upgraded to posi

but the carrier will be unique to posi or open

Thanks Tom, I seem to come across more posi carriers at decent prices as opposed to complete posi rear ends over here on the Left Coast... Every once in a blue moon one will come along at a bargain

Yep, converting ANY 65-72 12bolt housing to posi is super simple. All you need is the posi unit (Eaton preferred for street/perf use) and then of course, set it up. ZERO modifications are required.

I bought the 69 Chevelle with what I believe is a Buick 10 Bolt that was swapped in to replace the broken original 12 Bolt. It fits right in there. Is there a drawing link of the dimensions of the bracketing on the housing to help me confirm no mods were done? Thanks!

Rich, what you need to do when getting a new posi unit is first figure what gears it has and if you want to reuse them.I bought an eaton and they make 3 different sizes for the deck height for the ring gear,they do make spacers,so if you get the middle size and want to go up in size you can .If you buy the one for like 4;10 ratio you cant go down without getting a another carrier.Make sure you check your back lash even if you reuse your gears,because the new carrier is bound to be a few thousandths off.

Cool info... I have the 396/325 motor with the M20 and figure maybe the 3.55 or 3.31 ratio would be a good choice with the streetable hydraulic cam. Thanks!

Rich my 12 bolt was a one wheel peel and has like the 3;31 gear ratio in it and i too have a muncie with a little 350 for my motor and i got the middle carrier and reused my gears,because 4;10 ratio with a muncie is great green light to red light but not to good on the highway.so thats why i kept my original gears.Its pretty fun when you have low 3s and dump the clutch but hang on you wont be in the gas very long youll be in four different directions in a hurry!

I had a 68 El Camino with the SBC/M20 Muncie/3.73 Posi that put a smile on my face whenever I drove it... That was a few years ago... listed her in craigslist here and got a hit on her from a Swede! So she is now in Sweden with a lot of American Muscle from the old days... I still keep in touch with the Swede... He buys a lot of old cars from the Pacific Northwest. Sweden just loves our cars, but we gotta keep some here for us!

Anybody have the flange to flange (the flange welded to the axle tube) dimension? All I can find is what may be the face to face dimension of the axle flanges? Thanks!