'70 Buick Positraction: same as other GM?

[brad54]

I found a '70 buick Electra with Posi: is that going to be the same as other GM 12-bolt Posi units?

Is it worth the hassle of removing the carrier in a junkyard?

Brad

[Guest BJM]

Brad,

I'm not sure about the application issue but keep in mind that Electras, especially those with air conditioning, probably have ratios below 3:00 to 1 - not exactly muscle car ratios of 3:32 to 1 or higher.

[NTX5467]

In those earlier times, EACH GM division had their own rear axle designs. The Chevy designs were designed by Chevrolet for Chevrolet. From what I've seen, that was also the case with other GM divisions, too.

In the early 1970s time frame, there were some cross-line uses of rear axles in some of the GM big cars. In the case I'm thinking of, the Chevy rear axle had a "round cover" and the BOP axles had a "cut-out" cover.

On the issue of rear axle "cases" for the "open" and "Posi" rear axles, the flange which the ring gear bolts to is a specific thickness for a particular range of rear axle ratios. To compensate for the total build thickness of the gear and the flange it bolts to, if the flange is thin, the gear will be "thick", for example. This puts some definite limits upon which rear axle ratios will go with which "case" (open or Posi). This is where the aftermarket comes in with their "spacers" when you put deeper gears (i.e., 3.9) where a 3.08 used to be. This is where the hot rod nomenclature of "3-series" or "4-series" carriers come in.

I suspect that one reason that Buick rear axle is still there is because it's not a Chevy and it has a "cruiser" gear in it. If you pulled it out, you could probably sell it to somebody that might desire it. That would be your judgment call on that. It is what it is and could be valuable to somebody.

Just some thoughts,

NTX5467