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POSI interchange experts chime in please

Guest BJM

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I am getting a 72 Centurion this weekend (hopefully) with a 455 (of course) but it's been my experience that few Centurions were equipped with posis so I am "assuming" that it has an open 10 bolt rear axle.

I really want a numerically low posi back there so I can get better starts traction yet get decent highway gas mileage (read: 14 to 19 mpg)

What posis work as 1. drop ins for the 72 Centurion or 2. as pumpkins put into the axle housing?

Does the above 1984 posi work as either a drop in or guts only option? I see a lot of posis on Craigs List out of the 10 bolt cars built from mid 70's through 1990 or so but am unsure of what works and what does not. Please advise.

P.S. No this is not one I would consider due to 3.88 gearing but otherwise would have an interest. I would be looking for a "sweet spot" for gearing in the 2.92 to 3.42 max range. I am installing a prepped TH400 with higher 1st gearing for launches.

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The only direct swap rear axles will be something from a 71-73 (possibly 74-76) BIG BLOCK big GM cars. The rear end in the car is a 12 bolt 9 3/8 rear. Axle ratios available are 2.73, 2.93, 3.23, 3.42

If you want to try to make it easier, you might be able to swap in a rear end from a small block LeSabre, which is an 8.5" rear...and there are aftermarket gearsets for 8.5 corporate rears available.

Check out v8Buick.com for miles of discussion on this topic.

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  • 1 month later...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wildcat65</div><div class="ubbcode-body">I think I have a 2.93:1 out of a 74 Riv if you are interested.

Ted </div></div>

Would that posi fit into my '69 Electra?

Not that I have any problems with giddy up and I get 15 mpg as it is now....

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