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  1. #51
    Join Date
    Feb 2002
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    SW Ohio
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    Default Re: 9 3/8" rear differences

    I've had a chance to do some more research with the 9 3/8" rear. This applies to the 1971-75 version, which I run in both of my big block 76 LeSabres. This rearend design was gone by 76, but it fits up to 76.
    This started because I burned up another set of posi clutches in mine at the track. It kept wanting to spin the right side only with slicks in the waterbox. Then it would slowly try to engage itself as the right tire got hot and sticky. I would stop and start the burnout while really laying on the brakes trying to get it to lock up, but the damage was done. This is the second time, and fresh clutches only fix the problem for a short time. Seems the slicks in the water aren't providing enough resistance or torque load to energize the clutch pack, even though on the street it wasn't an issue.
    So I set out to replace that feeble "S" preload spring in the posi unit. The unit needs much more preload. After I would burn these things up, it would only take about 30 ft lbs to make it slip. Replacing the clutches would bring it back up to about 100 or so, but that is still not near enough for the track.
    I went through some posi unit parts I had and found some Eaton posi springs and spring plates. It looked like they would fit if the plates weren't quite as wide. So I narrowed a set and installed them with 400lb springs. The fit was good after modification, and it now took closer to 200ft lbs of axle torque to make the unit slip. But I was wanting more, and I was starting to worry about affecting the hardness of the plates with all of the welding.
    So with more digging through boxes of parts, I found a set of Auburn preload plates and springs for an Auburn posi 8.5" corporate GM application. Turns out the Auburn setup is a an exact drop in. Even the crossshaft was identical. In fact, I used the Auburn cross shaft. So maybe there is an actual use for the Auburn design, the rest of which I do not like. The cross shaft hole dia.(as mentioned above) and spring compression are perfect, as if designed for the 9 3/8" posi. The Auburns, with their cone type clutches, use lots of preload, so it was real fun to install. But I got it in and not even 600 ft lbs. of axle torque will make it slip. May need to find some lighter springs, but these are the plates to use.
    Here is a picture of the plates. From left to right. Stock Eaton plates/springs, then the narrowed Eaton plates/springs, then the Auburn plates/springs, and finally the stock feeble "S" spring with a picture of it installed.
    Attached Images Attached Images
    David Powell
    76 LeSabre 2dr 455 12.54@107
    76 LeSabre 4dr ht 455 14.50@93
    73 Riviera 455
    83 Regal 455 11.70@116

  2. #52
    Join Date
    Feb 2002
    Location
    SW Ohio
    Posts
    400

    Default Re: 9 3/8" rear differences

    Here are the narrowed Eaton plates installed. Perhaps I will end up putting these back in if I can't find lighter springs for the Auburn plates.
    Attached Images Attached Images
    David Powell
    76 LeSabre 2dr 455 12.54@107
    76 LeSabre 4dr ht 455 14.50@93
    73 Riviera 455
    83 Regal 455 11.70@116

  3. #53
    Join Date
    Feb 2002
    Location
    SW Ohio
    Posts
    400

    Default Re: 9 3/8" rear differences

    Here are the Auburn plates and springs installed. The fit is absolutely perfect, but this provides tons of preload- more than I was really looking for. It will probably chatter really bad. We'll see. I will be testing it soon.
    Attached Images Attached Images
    David Powell
    76 LeSabre 2dr 455 12.54@107
    76 LeSabre 4dr ht 455 14.50@93
    73 Riviera 455
    83 Regal 455 11.70@116

  4. Default Re: 9 3/8" rear differences

    Hey David, nice work- which track are you going to? I would like to see the LeSabre run. Ted
    Deceptively Proficient.

    Ted Nagel
    64 LeSabre Wagon
    65 Wildcat 4-speed
    65 Gran Sport 4-speed
    67 Wildcat
    68 GS 400
    69 GS Stage 1 4-speed
    70 GS Stage 1 4-speed

  5. #55
    Join Date
    Feb 2002
    Location
    SW Ohio
    Posts
    400

    Default Re: 9 3/8" rear differences

    Well, it works quite well. I tested my modified posi in many situations today. All of that preload had me worried, but it still slips as it should on dry road. In the grass or on gravel, it does scuff the inside tire some on a sharp turn. But on a dry road it feels fine.
    For one of two harsh tests, I put the right tire in the grass along the road, and kept the left on the pavement. I powerbraked it some, and it still smoked the left tire, which was on the road. That takes a good posi. For the other test, I gassed it hard during a sharp right hand turn to see if it would put the right rear up in smoke. That did not happen, I instead just ended up doing a 180 in the intersection. That takes a good posi also.
    I don't think I will have any more single tire burnouts in the waterbox. As for the chatter I was expecting with all of this preload, it's not a problem so far.
    David Powell
    76 LeSabre 2dr 455 12.54@107
    76 LeSabre 4dr ht 455 14.50@93
    73 Riviera 455
    83 Regal 455 11.70@116

  6. #56
    Join Date
    Feb 2002
    Location
    SW Ohio
    Posts
    400

    Default Re: 9 3/8" rear differences

    Hey Ted,
    Thanks. My obsession with the 9 3/8" rearend lives on. The car appears to be worthy of drag duty again. I've been going up to Kilcare dragway. It's closer to where I work. So I drive the car to work that day, then just head over there for test'n'tune. They have theirs on Thursday evenings. Otherwise it would be Edgewater. From my house, they are both the same distance.
    I guess there is also Tri-state. I've never ran there though, only watched. It's by far the closest, I just don't know very much about the place.
    Do you ever make it up to Kilcare?
    David Powell
    76 LeSabre 2dr 455 12.54@107
    76 LeSabre 4dr ht 455 14.50@93
    73 Riviera 455
    83 Regal 455 11.70@116

  7. #57
    Join Date
    Aug 2003
    Location
    wisconsin
    Posts
    183

    Default Re: 9 3/8" rear differences

    Wow Thats good info to know!!! Sounds like a real strong posi now!
    grandville464
    2010- 11.64 E.T- Best Mph 115.07- 60ft 1.63
    2011- 11.501 E.T 117.74 MPH 1.62 60 ft- 4550 pds

  8. #58
    Join Date
    Sep 2006
    Location
    Columbus, OH
    Posts
    59

    Default Re: 9 3/8" rear differences

    Does anyone know the difference between a 66 and 67 3.42 posi carrier? I have a 66 posi/gear set up and would like to swap it into my 67 and I'm under the impression that the LH carrier bearing is larger on the 67, but the pics at the beginning of this thread seem to contradict this. The carrier I have has both carrier bearings the same size. I haven't pulled the cover off to examine the bearings yet. If the bearings are different, are the carriers the same, but just a different bearing used. Anyone know? Thanks

  9. #59
    Join Date
    Feb 2002
    Location
    SW Ohio
    Posts
    400

    Default Re: 9 3/8" rear differences

    Look closely at the pics again. The left bearing(against the floor) is not so much bigger in diameter, it is wider- which would appear as height in the picture since the units are on their ends. So your original impression is correct.
    David Powell
    76 LeSabre 2dr 455 12.54@107
    76 LeSabre 4dr ht 455 14.50@93
    73 Riviera 455
    83 Regal 455 11.70@116

  10. #60
    Join Date
    Sep 2006
    Location
    Columbus, OH
    Posts
    59

    Default Re: 9 3/8" rear differences

    The posi I have on my garage floor has both bearing races the same size, .650" x 3.065"OD and the bearings appear to be the same as well. So this must be a '66 unit, correct?
    Will this '66 posi/ring/pinion swap into my '67 if the bearings are changed to the '67?
    1967 Riviera
    1999 Riviera
    2006 TrailBlazer SS (14.05, bone stock)

  11. #61
    Join Date
    Nov 2007
    Location
    Fargo, ND
    Posts
    68

    Default Re: 9 3/8" rear differences

    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?
    '73 Buick Estate Wagon 455

  12. #62
    Join Date
    May 2003
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    I-95, Old exit #69 ;]
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    5,309

    Default Re: 9 3/8" rear differences

    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"

  13. #63
    Join Date
    Nov 2007
    Location
    Fargo, ND
    Posts
    68

    Default Re: 9 3/8" rear differences

    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?
    '73 Buick Estate Wagon 455

  14. #64
    Join Date
    May 2003
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    I-95, Old exit #69 ;]
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    5,309

    Default Re: 9 3/8" rear differences

    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.

  15. #65
    Join Date
    Sep 2004
    Location
    Michigan, USA
    Posts
    15,232

    Default Re: 9 3/8" rear differences

    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
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  16. #66
    Join Date
    Jan 2003
    Location
    Connecticut
    Posts
    5,492

    Default Re: 9 3/8" rear differences

    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!
    Ken Lisk
    Happiness is a long smokey burnout.
    '71 Limemist GSX, Restored 2010 by Gran Sport Garage, aka Nick Serwo
    '72 Riviera, Crystal Blue
    '63 225 'Vert Bahama Blue
    BPG# 1409
    NE-GS/GN Member
    ROA Member# 12258
    GSCA Member# 1176
    AACA Member# 993257

  17. #67
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    May 2003
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    Default Re: 9 3/8" rear differences

    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.

  18. #68
    Join Date
    Jan 2003
    Location
    Connecticut
    Posts
    5,492

    Default Re: 9 3/8" rear differences

    Quote Originally Posted by bob k. mando View Post
    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.
    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?
    Ken Lisk
    Happiness is a long smokey burnout.
    '71 Limemist GSX, Restored 2010 by Gran Sport Garage, aka Nick Serwo
    '72 Riviera, Crystal Blue
    '63 225 'Vert Bahama Blue
    BPG# 1409
    NE-GS/GN Member
    ROA Member# 12258
    GSCA Member# 1176
    AACA Member# 993257

  19. #69
    Join Date
    May 2003
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    I-95, Old exit #69 ;]
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    5,309

    Default Re: 9 3/8" rear differences

    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.

  20. #70
    Join Date
    Jan 2003
    Location
    Connecticut
    Posts
    5,492

    Default Re: 9 3/8" rear differences

    Quote Originally Posted by bob k. mando View Post
    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.
    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!
    Ken Lisk
    Happiness is a long smokey burnout.
    '71 Limemist GSX, Restored 2010 by Gran Sport Garage, aka Nick Serwo
    '72 Riviera, Crystal Blue
    '63 225 'Vert Bahama Blue
    BPG# 1409
    NE-GS/GN Member
    ROA Member# 12258
    GSCA Member# 1176
    AACA Member# 993257

  21. #71
    Join Date
    Apr 2002
    Location
    Worcester, MA
    Posts
    3,042

    Default Re: 9 3/8" rear differences

    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

  22. #72

    Default Re: 9 3/8" rear differences

    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.
    Adam Martin
    BPG# 1358
    BCA# 39765
    1970 Buick Skylark Custom 455 Coupe
    www.antiqueautomotiveservice.com

    http://www.antiqueautomotiveservice.com/images/logo_top.gif

  23. #73
    Join Date
    Aug 2003
    Location
    wisconsin
    Posts
    183

    Default Re: 9 3/8" rear differences

    Quote Originally Posted by 71GSX455-4SPD View Post
    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!

    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!!
    grandville464
    2010- 11.64 E.T- Best Mph 115.07- 60ft 1.63
    2011- 11.501 E.T 117.74 MPH 1.62 60 ft- 4550 pds

  24. #74
    Join Date
    May 2008
    Location
    about 40 miles from Vienna, AUSTRIA
    Posts
    320

    Default Re: 9 3/8" rear differences

    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)
    ________________
    Peter

    Just back from San Francisco - L.A. - Las Vegas trip.
    2500 miles in 18 days.
    Saw no nice Buicks on 10th Aug. in Pomona
    But many Impalas with AirRaide :-(

  25. #75
    Join Date
    May 2003
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    I-95, Old exit #69 ;]
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    5,309

    Default Re: 9 3/8" rear differences

    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_st...0Style%20Chart

 

 
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