9 3/8" rear differences

Discussion in 'A boatload of fun' started by quicksabre, Apr 22, 2005.

  1. boristheblade

    boristheblade Nutcase

    I've got a line on a posi out of a '76 Estate Wagon. The owner says it is a 4 coil spring type. Anyone have an idea what this beast is, and would it work in my '73 Estate?
     
  2. bob k. mando

    bob k. mando Guest

    Anyone have an idea what this beast is, and would it work in my '73 Estate?

    you need to verify that both rear ends are either 9 3/8" or 8 7/8". you can't swap parts between those rears.

    my rear end codes don't show a 9 3/8" available past 1972, so you might be all right with both of them being 8 7/8"
     
  3. boristheblade

    boristheblade Nutcase

    So at the factory, everything in Buicks went to 8 7/8" '73-76?
    I found another carrier out of a '73 Olds, and the seller only has the bare carrier, no gears. Is there a page to check casting codes or were they also of the Pontiac design '73-76?
     
  4. bob k. mando

    bob k. mando Guest

    I found another carrier out of a '73 Olds, and the seller only has the bare carrier, no gears. Is there a page to check casting codes or were they also of the Pontiac design '73-76?

    i have a collection of info on a spreadsheet that i've gotten from different sources.

    the 9 3/8" is an Oldsmobile design, the 8 7/8" is Pontiac.

    my Buick 1973 page doesn't have any codes for the Olds rear, neither does my Oldsmobile 1976 page. all the big car applications decode as Pontiac.

    but i can't guarantee that there aren't Olds rears in some of those cars, i believe i've seen people say that they were in production longer than that.



    carrier out of a '73 Olds

    just because a car is of a particular brand doesn't have anything to do with which factory produced the rear end that's underneath it.

    take the 8 1/2" rears for an example:
    a 1973 Buick A-body could come with an 8 1/2" housing that had been produced by Chevy, Detroit Axle, Oldsmobile or even Buick.
     
  5. DaWildcat

    DaWildcat Platinum Level Contributor

    Here's an update due to something Kimson (EEE) found out the hard way.

    Looks like his 1966 Wildcat actually had what parts we've been thinking Buick used starting in 1967 - the larger carrier bearing on one side.

    A quick look at my parts book confirms it...the 1966 listings are clearly specifying different housing numbers for a "1st type" and a "2nd type" meaning they made a mid-model year change. This means the only way to know what's up for a swap would be to ID both your housing and the donor housing if you're working on a '66 Wildcat/Electra/Riviera.

    Devon
     
  6. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    So, what about Cadillac? Different animal than the BOP altogether? Will a 3.42 posi out of a '76 DeVille bolt up to a '72 Riv? And if so is it a straight swap in? What about strength? Is it inferior to the mighty 9 3.8?

    Anybody have experience with this?

    Thanks!
     
  7. bob k. mando

    bob k. mando Guest

    Will a 3.42 posi out of a '76 DeVille bolt up to a '72 Riv?

    if you swap the entire housing drum to drum, i believe so. every data sheet i've ever seen only makes exceptions for the wagon rear ends on the full size cars, as those were designed for leaf springs.

    there is a good chance that you'll be converting from 9 3/8" to 8 7/8" though.

    take some basic measurements on mounting points, spring perches and drum face to drum face width.



    Is it inferior to the mighty 9 3.8?

    it's "inferior" in that there's no way it's as strong as a 9 3/8". you can't hardly make up a 1/2" difference in steel on 'advanced' design.

    it should be plenty tough for whatever you want to do though.
     
  8. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Thanks, Bob, I'll do some measurements today and compare to the possible donor rear. It would be an entire drum to drum swap that I'd be considering. So, not as strong as a 9 3/8, but stronger than the corporate 8.5 I guess. Probably as oddball as the 9 3/8 in terms of parts too?
     
  9. bob k. mando

    bob k. mando Guest

    Probably as oddball as the 9 3/8 in terms of parts too?

    oh yes. we've been over that many times. but if you've got the posi and ratio you want it doesn't matter much.



    every data sheet i've ever seen only makes exceptions for the wagon rear ends on the full size cars


    didn't complete my thought. the above statement applies to full size Buicks from 1971-76. i know there are some earlier year Rivs that have Panhard bar suspensions, they wouldn't be compatible either.
     
  10. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Thanks for the info, Bob. I've taken a number of measurement on the current rear (backing plate to backing plate where the axle tube meets- 60 in, LCA mount to LCA mount inside width between flanges- 43 3/4 in, shock to shock centerline 40 3/8 in, and spring perch to spring perch centerline 38 in) to make sure all lines up.

    This car will be a full weight '72 Riv with a 400+ horse motor, a 2700 or so stall converter and a 3.42 rear. Should be a nice upgrade over stock!
     
  11. bobc455

    bobc455 Well-Known Member

    One more question that I haven't seen addressed.

    I am considering a project to put some big HP into a big car. The car has the 9-3/8 rearend with a 3.42 posi, from a '73 Riv GS.

    The "usual" assumption is the bigger the better, so if a standard 12-bolt rearend can handle X horsepower, can the 9-3/8" handle more than X horsepower? Or is there a weak point in these rearends that might not exist in the 12-bolt rears?

    Anyone ever managed to break one of the big rearends?

    -Bob Cunningham
     
  12. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    I don't know the breaking point of these rears...

    If the rear end you have really did come from a 73 Riv GS, then it's more than likely a 3.23.
     
  13. grandville455

    grandville455 Well-Known Member


    I have raced my grandville for 4 yrs with the buick rearends and not one failure... last yr pulling 1.77 60fts!.. this yr I have stepped up to aluminum heads and a roller cam.. making around 525 hp!.. and 600 ft pds!!.. so well see track opens on the 11th!.. stay tuned!!
     
  14. austrian455

    austrian455 6.56 $/gal...still 455

    A friend of mine is going on a junkyard tour in the US.
    I told him to look for a Posi for the Centurion.
    What car could have a bolt in rear for the centurion?

    71 - 75 le sabre
    71 - 76 electra
    71 - 75 wagon

    71 - 75 olds delta 88
    will a 98 rear also fit?

    what about pontiac rears?
    did 71 - 75 full size pontiacs use the same rears?
    (catalina, bonneville, grand ville)
     
  15. bob k. mando

    bob k. mando Guest

    71 - 75 wagon

    the wagons have a leaf spring suspension. you could take the carrier and ring/pinion but you can't "bolt in the rear" drum to drum assembly as long as you get the correct rear. both 9 3/8" and 8 7/8" rings were used in this period.

    there are also 8 1/2" rears in the small block, mid-sized cars. these have the advantage of tons of gear sets, carriers and bearings. the Le Sabre is the Buick "mid-sized" model.


    what about pontiac rears?

    Pontiac, Olds, Cadillac and even Chevy big car rears will work from 1971-76.

    http://www.classicbuicks.com/body_style.htm#1971-1975 GM Body Style Chart
     
  16. Lucy Fair

    Lucy Fair Nailheadlova

    I wanted to ask a question about shafts,if i have 3.07 open diff and i put there 3.07 posi will shafts work?
     
  17. quicksabre

    quicksabre Well-Known Member

    Yes, the axle shafts are the same.
     
  18. DaWildcat

    DaWildcat Platinum Level Contributor

    Just noticed some more interesting 9-3/8" detail according to my parts book...sorry if it's already been mentioned.

    I'm finding some gearsets w/the same part numbers from 1965-1970. We know carriers changed within those five years, but can anyone confirm gear commonality?

    I'm seeing some interesting ratios, too:

    2.56:1 1967-1970
    2.78:1 1965-1970
    3.07:1 1965-1969
    3.23:1 1965-1966 (three different part numbers for this ratio)
    3.36:1 1965
    3.42:1 1965-1970 (three different part numbers for this ratio)
    3.58:1 1965
    3.91:1 1965-1970
    4.45:1 1965

    Something else - in 1965 the gearset part numbers are different between posi and open carriers. :Do No:

    Devon
     
    Last edited: Jun 13, 2009
  19. polaris

    polaris hot rod

    looking for rear axle that will fit under my 1956 buick special??? needs to have 5 on 5 bolt pattern and a tail ratio. my 56 has a closed drive shaft want to update.:Dou:
     
  20. DaWildcat

    DaWildcat Platinum Level Contributor

    Try posting your question in the "Got Gears?" forum, since this thread is specifically regarding the 9-3/8" rear axles. There will probably be better, more modern options than trying to adapt one of the big car rear ends.

    Devon
     

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