72 Centurion Posi Traction

[Austrian455]

Is it a Posi ?

[EEE]

There is a tag on one of the bolts on the diff cover that indicates it's a posi, that could of course have been removed at some point, bt it would be the easiest way to see. Otherwise put it on jack stands so both tires are in the air. Then put it in neutral and spin one wheel, if the other wheel spins in the same direction it's a posi.

[Austrian455]

OK, very old thread as you can see, but not needed to create a new one.

Now I know, I need a Posi.
So I´ve got some questions:

1) How to get one? Can anyone offer me one?

2) Where to get a rebuild kit for those?

3) Can I use my old ring / pinion set? I love my 2.92 ;)

4) Is there a good solution for a axle swap? I don´t want to cut
or weld on the car.

5) I´m 99.9 % sure that the answer to this question is no. But
trying is free ;)
Can I purchse any aftermarket posi or new ones? (Auburn, Detroit Locker....)

6) What would be a good price for a useable posi with good ring/pinion set?

[73 Centurion]

There have been threads here and on the V8 Buick board about the variety of axles Buick used under the full sized cars.

If you have a 455 the most common posi axle was 9 3/8. Often this is referred to as a 12 bolt. The 12 bolts are not on the cover, but inside the axle. There are 10 bolts on the cover which makes it easy to confuse with the "10 bolt" axle which is a different beast. Not to confusing eh?

There is very little aftermarket support for the 9 3/8 axle. I beleive the ring and pinion gears do not swap between all axles. I think the posi's all had at least 3:1 gears or higher. Your 2.92 will probably not work. On the positive side they have a reputation for being bullet proof. Pontiac's seem to be the best place to look for a full size posi. I think the Riviera axle will fit, and they are more likely to have posi. I think Chevy axles used different universal joints.

I have a 350 with a posi and I haven't been able to definitely pinpoint what kind of axle it is. There have been stories of 8.5 or 8.8 inch axles under full sized cars. There is aftermarket support for these. If you can find one you could upgrade it to posi and have a choice of ratios.

These axles are huge, and heavy. Shipping is going to be expensive.

Your best bet is to read everything you can find on full size GM axles. Learn to identify what you can by their exterior. The final test is to jack up the rear so both wheels are free. If you spin one tire and the other goes in the same direction you have found a posi. If it spins in the opposite direction it is not.

John

[Austrian455]

As my car is a 72 it´s of course a 455. I know that it´s the 9 3/8 axle.
My problem is that (as you can imagine) we don´t have junkyards with old US cars here in Austria. I knew about one guy who parted out a 75 Impala 400.
I thought that a car equipped with the 400 cui engine should have a posi. But those chevy didn´t use the 9 3/8 or did they?
But I think the complete axle of the Impala could be interchangeable.
I have to call him and see what he has.

[Robroy]

Yankee Parts in Sweden Gothenburg offers 10-bolted 2:73 GM 1971- posi rear for 330€ plus tax. You would probably get away with paying the Austrian tax only.
Their catalogue doesn’t say if they ship abroad or not but you could shot them an e-mail and ask info@yankeeparts.se

[EEE]

It's tricky to find posis, I've stuck my nose under fifty old Buicks maybe and one has had a posi. I've found two more on Oldmobiles which seems to be the same kind. There's a long thread about the large axles here:

http://v8buick.com/showthread.php?t=71740

Not all of this info relates to your axle, but there's plenty of good info in there.

The best deal is to swap out the entire axle it seems, unless you know how to re-install gears which requires some advanced knowledge. Check the thread, and keep your ears open in the for sale section at the v8buick.com site. A 3.23 > 3.42 posi axle will probably run about $4-500. I think someone even got over a grand for one once. If you're ok with the 2.93s, you might get it cheaper with some luck.

[Austrian455]

Kimson, thanks for the info
Ohh man, a grand? you mean 1000 USD for a Posi???
Holy ****.
I know it´s everything else than a nice job to re-install a ring/pinion set.
But I can do it my self. If you like, check out my thread about my 57 Bel Air resto.
There you can see how I installed a new posi and 3.08 gears in the old 10 Bolt chevy rear. That was the first axle I ever did. I bought all the tools and it took me many hours and trys to to be happy with the tooth contact pattern. Now I´m happy I did it. I want to be able to tell people I did everything by my self.
Also on the Centurion.
You said that you pulled a posi out of a Buick and two out of oldsmobiles.
Is one of them for sale? :Brow:

[Austrian455]

I found a 8.5 10 bolt out of a 74 electra.
It´s a c-clip axle. Is this a desirable axle?
Will this fit the Centurion? I would say yes, but want to be sure.
I want to use the orig. brakes my Centurion has now.
Will they fit?

[Eric B]

I've read all the previous posts. I have and have had a lot of early 70's full size Buicks. I've never seen one or heard of one without 12 bolts on the cover but I am not an expert. I bought a 2.93 posi from an Electra for $100 a few years ago as a spare and I bought a 3.42 posi from a Riviera for $200 a few years ago that I put in my Centurion. So I know they are out there. If I thought mine was worth $1000 I would sell it tomorrow. Cheers.

[Austrian455]

Do you still have the 2.93 posi ?

[Eric B]

Do you still have the 2.93 posi ?

Yep. I agree with Kimson, check V8Buick.com or place a want ad. I got one from a want ad in the GSXtra. Just put the word out.