Posi Identification Need Help

[centurion 455 ragtop]

I was cleaning out the garage today and found buried under the work bench an old rear unit that I was traded for other parts way back in the mid 80's. I remember I was told it was a posi unit that would fit my '73 Riviera.

Question, I never installed it or checked the validity of it. The Riv is long gone but now I am searching for a posi unit for my '73 Centurion and may have discovered it was here all along under my nose.

Did searching, am I correct to say it is a posi unit that will fit B,C, E Series Buicks for '73-75. That being for a 9 3/8 rear. Seems to look the same as the one shown in the Illustration Catalog for Buicks though 1975.

If so, now to get some gears. Currently I have an 9 3/8 open rear with 2.73 gears in my Centurion. Need to know can I fit a set of 2.93, 3.08's or slightly larger for this carrier? Yes, Yes I know I have a better chance on seeing Jesus walk on water before I can find a set of 3.23's for this carrier. Just would like to know if this posi carrier will fit and what gear options can I go with.

The ring gear attached has 41 teeth on it with a part number 41B14 GM DT 2882 I have no clue on what ratio. And the only other numbers stamped I can find is #761, which is on the carrier . Need some help here. Photos attached

[centurion 455 ragtop]

shot 2. OK did my own searching it is a posi unit that will fit B,C, E Series Buicks for '73-75. Now to gert some gears. Currently I have an open rear with 2.73 gears. Anyone know where I can get a set of 3.08's or slightly larger for this carrier?

[Smartin]

That's a 2.93....

measure the ring gear...make sure it's 9 3/8. That one does look just like the one I had a couple years ago.

[centurion 455 ragtop]

That's a 2.93....

measure the ring gear...make sure it's 9 3/8. That one does look just like the one I had a couple years ago.

Adam

It does measure out to a 9 3/8. Next question. Can I use this 2.93 ring gear with the pinion gear of my 2.73 rear, or is it I need an entirely new 2.93 ring and pinion set.

[Smartin]

You need to have a matched ring and pinion set, I would imagine. That is a good question for oPh on the v8 board.

[EEE]

Sure looks like the real deal.. Finding ratios means going to the yard and checking cars, there's hardly any gears floating around at the super market. Best bet for steep numbers might be if someone is parting out a gs riv from 71-73 (>76?)

[centurion 455 ragtop]

The hunt begins! Thanks for the help guys.:xyxthumbs:

[72gsx4me]

I have been reseaching for a while and finding ring and pinion over 2.93 is surely a battle. In my exploration, I did find that most 1971 to 1976 B body cars with 9 3/8 were more likely to have taller gears when they had a small block. I have seen many b body Buicks in salvage yards with a 350. That almost always equates to at least a 3.08 ring and pinion. I am almost positive that I saw a 72 Electra 350 in Vans Auto Salvage in Wisconsin. He also had a boattail Riv, and a 71 Centurion Hardtop. Also remember that a 71 to 76 Pontiac Catalina, Bonneville or a Olds Delta are candidates for 9 3/8.

Hope this helps.

Will:cool: :cool:

[Brad Conley]

Wouldn't have been a '72 Electra with a 350, unless someone put it there after the fact. 455's were standard through 1976 in the Electra series.

[centurion 455 ragtop]

True Brad, but there we're a poop load of LaSabre,s and the 73 Centurion which the standard engine as we all know was a 350. Never realized to look at the small block big cars. I'll settle for 2.93's or 3.08s.

[Smartin]

Small Block B bodies should have the smaller rear...not the 9 3/8

[72gsx4me]

Have done more digging and the Grand Poo Bah is correct. The Lesabres have a smaller ring and pinion. The rearend housings are the same but the ring and pinion is different.

See http://www.ratechmfg.com.

1973 Buick Service manual shows Lesabre with 8.5 ring gear, but Ratech shows it to be a 8.875.

If Ratech is right, is it possible to use a small block lesbre carrier with the 8.875 12bolt Chevy ring and pinion gears? If so, the options are blown wide open.

I wish I had a Lesabre 350 rear end lying around cause I do have a set of 12 bolt 3.08 gears in my garage. It would be interesting to see if it would work.

[centurion 455 ragtop]

[QUOTE=72gsx4me;
1973 Buick Service manual shows Lesabre with 8.5 ring gear, but Ratech shows it to be a 8.875.

If Ratech is right, is it possible to use a small block lesbre carrier with the 8.875 12bolt Chevy ring and pinion gears? If so, the options are blown wide open.

I wish I had a Lesabre 350 rear end lying around cause I do have a set of 12 bolt 3.08 gears in my garage. It would be interesting to see if it would work.[/QUOTE]

Now I am confused. So this means that all 73 LeSabre's also had a different rear than the 73 Centurion? Both are same size cars sharing most parts. If so then what size rear would a 1973 350 Centurion have. I would have thought a 9 3/8

[Smartin]

Rick, got a 1973 chassis manual?


I didn't realize the housing was the same size in both 8.5 and 9 3/8...that doesn't seem to jive. I can't be sure of anything, though. This is one of those times when I wish I had my LeSabre at home to compare.

Does anyone have a 350 Centurion to check, maybe take some pictures? Count the bolts holding on the rear cover? The 9 3/8 covers have 12 bolts.

[72gsx4me]

These B Body rear ends are very confusing.

Here is more fuel to the fire. Srecko had 2 1973 Buick Centurion 455s at one time. Both his black Centurion and Green Centurion had 455s and both had the same rear end. 10 bolt cover with a 12 bolt 9.375 ring and pinion. The Green parts car had a 2.73 posi so he has that on the side in his garage.

I know where there is a 1973 Buick Centurion 350 parts car and I have been thinking about buying it for parts. It has the 3.08 cause I saw that on the build sheet. I really didn't take a close look at the rear end though.

Good rear end pictures of a 350 b car vs a 455 b car would be great.

Anyone have any? :confused:

[centurion 455 ragtop]

The 2.73 ratio is listed as an economy option, my slug has it. Hope this helps a bit. As far as the parts cars I guess the only way to be sure is the tags and stampings on the differential

[72gsx4me]

In reviewing the Hollander book, the best best for high ring and pinion gear for a Buick 455 Centurion would come from a 1971 to 1975 Riv GS. 1971 and 1972 will be the 3.42 and 73-75 will be 3.23.

Let me know if you need anything from the book. Great info.

ie. Rear brakes for the Buick Centurion 9 3/8 are same as 1991 Chevy Caprice.

[EEE]

ie. Rear brakes for the Buick Centurion 9 3/8 are same as 1991 Chevy Caprice.

I was looking at that after I read an article in car craft about b-body brake interchangeability. Since the cop cars had discs in the rear on the early 90's caprices, but it would take some figuring out if it would actually work. I was sitting there looking at one in a yard, but without measurements or the chance to just try and fit stuff, I couldn't really tell.

[72gsx4me]

I don't think the rear disk brakes would work. I don't think the housing ends are the same. The drum brakes would work as Hollander said, but that is because it is a 5 inch big car bolt pattern.

If your thinking about a rear disc brake conversion, let me know. I am working with TSM Manufacturing to get a set or two made. The kit is about $650 to $750. They need exact measurements of bolt circle and other measurements to come up with bracket, but they say it is possible.

:cool:

[centurion 455 ragtop]

In reviewing the Hollander book, the best best for high ring and pinion gear for a Buick 455 Centurion would come from a 1971 to 1975 Riv GS. 1971 and 1972 will be the 3.42 and 73-75 will be 3.23.

Let me know if you need anything from the book. Great info.

ie. Rear brakes for the Buick Centurion 9 3/8 are same as 1991 Chevy Caprice.

Regarding the Hollander book, is it book #49 that covers 1973-1983? I am looking to get a hold of a copy, just need to know if I am on the right track. photo below.

[72gsx4me]

Rick,

I went to Hollander.com and got a 3 book set. It covers 1965-1979. There is a Body parts book, a Chassis book, and an Engine book. I did not buy the big book. These three books had everything that I wanted and the years that I wanted. I think the 3 book set cost about $120 delivered.

Will:cool:

[centurion 455 ragtop]

THanks for the info Will:xyxthumbs: