Rear differential

[takis]

Looks like my rear differential is shot...I have a 73 Centurion 350 conv ...was curious as to what is the length was on the axel. What would be easier to do, just replace the axel, and if so what model car could I exchange it out with. I have tried looking all over the states for a Centurion axel, cant find one in good condition. Any advice would be greatly appreciated. :xyxthumbs:

[EEE]

Where are you located, and how picky are you with the gear ratio?

[takis]

Orlando Fl, would like to get the gear ratio as close as possible, dont want it sittin in first gear for the first 50 miles...:beers:

[EEE]

I asked someone over at v8buick.com if he knew of any car at the yards in Fl. This was hi reply:

"Nothing here in the local yards...but any full size model 71-6 will have the rear he can use. He should try LKQ in Orlando on SR50 ... they may have one...they go through many cars."

Not sure what LKQ is, but it might be worth looking into.

I would take the whole axle and swap it out in one piece, should run you about $80 at the yard once you find it, unless it's just an axle shaft or a bearing that's gone.

[Robroy]

Contact Dennis (Heavycenturion) and see if he still has his 72 parts car, he’s in Athens GA.

http://www.buickcenturion.com/forums/showthread.php?t=1045

[73 Centurion]

Hi there,

Positraction axles are rare but they do exist. If you can jack up the back of your car so both rear wheels are off the ground you can see if you have one.

As you spin one tire watch the other one. If it turns in the same direction shout "yippee" because you have a posi. If it turns in the opposite direction you don't have posi.

If you have one of the rare posi's it's worth repairing, or at least sell it to someone who is willing to fix it.

This test is a good one to know if you are searching the salvage yards. Pontiacs are more likely to have a posi than the other brands. You can also keep an eye out for a rear sway bar. If you're swapping the axle adding the swaybar is not that much more work. Just be sure you grab the lower control arms along with the bar.

Good luck and let us know how it works out.

John

[Austrian455]

It would be a big suprise to me if he has a Posi in a 350 car. It´s possible, but who would order a 350 and a posi ?!?
I read something about some wagons on a yard at v8buick.
Those wagons also had posi units often.
If I find the thread I will post it.

[Austrian455]

http://www.v8buick.com/showthread.php?t=173913

[takis]

Hey guys, awesome info, called LKQ yards, they dont have anything cataloged but going there this weekend...keep the advice going ..again thanks

[EEE]

Bring a small jack if you have one, you might also be able to use one that you find in a trunk somewhere. You'll need it to take the springs/shocks out. Also good to support the axle when it comes down. Also bring a socket set so you can work with two wrenches on either side of the control arm bolts. A breaker bar could be good to have too, the bolts on the rive shaft connection can be quite tough.

If it's the larger 9 3/8 axle you're going for (12 bolts on cover, 12 bolts on ring gear), then you might have to take the drums also, not sure what the difference might be there in comparison to the smaller axle found in the 350 cars. Look for 71-76 big Buicks.

Good luck.

[nick rabi]

Bring a small jack if you have one, you might also be able to use one that you find in a trunk somewhere. You'll need it to take the springs/shocks out. Also good to support the axle when it comes down. Also bring a socket set so you can work with two wrenches on either side of the control arm bolts. A breaker bar could be good to have too, the bolts on the rive shaft connection can be quite tough.

If it's the larger 9 3/8 axle you're going for (12 bolts on cover, 12 bolts on ring gear), then you might have to take the drums also, not sure what the difference might be there in comparison to the smaller axle found in the 350 cars. Look for 71-76 big Buicks.

Good luck.

Drums,brakes & mounting are the same on the 9 3/8 12bolts & the 8.5 10 bolts .Also 71 -76 big car Chevy,Olds or Pontiac will work. A non posi 9 3/8 should be very easy to find,a posi will be a little more difficult to find.

[Smartin]

I've been under the impression that 350 cars had 8.5" rears.

[EEE]

They do, ten bolts on the cover. I think the later 74-76 cars with the 455 might have that rear too.

[Robroy]

I think the later 74-76 cars with the 455 might have that rear too.
I have the ten bolt cover on my 73 (455)….

[73 Centurion]

I know of 1 Centurion that came with a 350 and a posi. Mine. I thought it was a weird combination, but I'm happy to have it.

There have been extensive threads on the combinations of axles under the full sized Buicks. I haven't been able to determine exactly what is under my car. The external signs don't seem to be definitive.

I've read about 8.5", 9 3/8" and a few odd balls called 8.75".

I think the ultimate would be an 8.5". Simply because the parts supply is far greater for those than the others.

The 9 3/8" axles are supposed to be bomb proof, but it's hard to find and your choice of ratio's is limited.

John

[takis]

ok, so I have checked every junk yard and I think I have found a comparable Diff, what do you guys think if I pulled the Rear Axle from a 76 Cutlass Brougham, you guys think that might be a good fit ? Checking the car out tomorrow. Nothing like spending a Saturday morning with a couple of friends at my local Pull and Pay.

[pphil]

I have the ten bolt cover on my 73 (455)….

the buick 9 3/8 rear 12 bolt rears have 10 bolts on the cover
just some usless information
scott

[Smartin]

The 71+ 9 3/8 rears have 12 bolts on the cover. 70 and earlier have 10.

[73 Centurion]

The oldsmobile axle should fit fine. If you're really lucky it's a posi, but it sounds like you need something functional first.

With patience you'll be able to find the posi you need, but it will take time and luck.

If you can find a full size GM (other than Cadillac) with a rear swaybar it will help some with traction. The wheel that receives the power will try to rise and the swaybar helps push it back down. It's not as good as a posi, but better than nothing. It's also easier to find and will still be worthwhile when you do find the posi.

John

[pphil]

The 71+ 9 3/8 rears have 12 bolts on the cover. 70 and earlier have 10.

thanks
see i learn something every day
scott

[takis]

Woo hoo ..my baby is back on the road, took me a bit but I found me a road side mechanic in Geneva Fl. Several shops quoted me prices from $1800 to $1200, the road side mechanic who had a garage that would smoke most shops fixed it for a whopping $570, totally replaced the ring and pinion with a 3.08 and she drives like a dream. Its been a rainy two weeks in central Fl but it looks like a sunny saturday and gents ya better believe I am dropping the top and enjoying the ride.