9 3/8" rear differences

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

  1. quicksabre

    quicksabre Well-Known Member

    I've been tracing some differences worth mentioning between various 9 3/8" rears. First, a recently discussed issue concerns the 67-70 big rear asking if a 3.07 posi carrier can be used with a 3.42 gear. The answer is NO, at least not without a ring gear spacer. My 67 Riv has a 3.07 gear. I spotted a 70 Riv with a posi this week at a local yard. I removed the posi, and grabbed the gears also since they were 3.42. I was planning to install this posi with my 3.07 gears, not really wanting a 3.42 for the highway. Good thing I grabbed the gears, because the carriers are DIFFERENT. This actually makes good sense because with the 71-75 big rear, the 2.73-3.23 carrier is different from the 3.42 carrier.
    See in the picture, the gear mounting flange is a different height. These are both 67-70 carriers, the posi was used with a 3.42, and the open carrier was used with a 3.07. They are different. I will go ahead and use the 3.42 gears so that I can make use of the posi, and run some really tall tires to tame it.

    Attached Files:

  2. quicksabre

    quicksabre Well-Known Member

    Here is a close up of the difference in flange height. It' approximately .175". Both carriers are sitting on their ends on a level surface, not resting in any way on the bearing.

    Attached Files:

  3. quicksabre

    quicksabre Well-Known Member

    Next, I am comparing the 67-70 design with the 71-75 design. There have been questions as to whether the carriers interchange. Again, the answer is NO. 67-70 rears are 30 spline, 71-75 are 31 spline. My 67 axle falls right through a 71-75 side gear. In addition, the left bearing on a 67-70 carrier is much bigger than the right one. Both sides are the smaller bearing for 71-75. Is it just the bearings? Again NO. The neck diameter is the same, so you could technically run two small bearings on a 67-70 carrier, but the length of the neck is longer on the left side for the bigger bearing. A spacer would be needed.
    Also, the ring gear flange height changed again. In the picture is a 2.73-3.23 71-75 carrier sitting next to the 67-70 3.42 posi. The flange height oddly enough is nearly the same, when it should be approximately .175" lower. Even getting beyond all of this, you would still need to deal with the difference in spline count by playing with side gears. But I don't think you would get very far with this because the 67-70 posi is clearly an Eaton design, while the 71-75 posi is clearly not an Eaton design, so the side gears, clutches, etc are totally different.
    Bottom line is that just about every question having to do with the big rear can be answered with a NO, including parts availability. Much scavenging is required to support these rears. I have been lucky enough to find a 3.42 posi and a 2.93 posi for my 76 LeSabres, and now a 3.42 posi for the 67 Riv. But it has taken some searching. At least the bearings and seals seem to be available. I have even bought rear cover gaskets through NAPA for both types. A good way out on the 71-76 cars is to find an 8.5" bolt in axle version, for those have good parts availability. I have not been forced to go this route yet. But up to 70, there really is no alternative to scrounging.

    Attached Files:

  4. jamyers

    jamyers 2 gallons of fun

    Wow. Thanks for doing the legwork on this!!! :TU:

    This needs to be a Sticky!

    Now to save this thread to hard drive...
  5. jamyers

    jamyers 2 gallons of fun

    9 3/8 rear housing differences

    To add info about the big rear housings, summarized from the 2 or 3 other discussions:

    It looks like there were 5 versions of 9 3/8 rearends, in 3 "generations", and nothing from one generation will interchange with another generation:

    '66 Riv: One UCA and a panhard rod, L & R carrier brngs same
    '66 E/L/W: 2 UCA and no panhard rod, L & R carrier brngs same

    '67 to '70 Riv: One UCA and a panhard rod, L & R carrier brngs different
    '67 to '70 E/L/W: 2 UCA and no panhard rod, L & R carrier brngs different

    '71 to '73 ALL: 2 UCAs and no panhard rod, L & R carrier brngs different

    The '70 rear end housing won't go into a '71 car, because the mounting ears for the control arms are in different places.

    Only one question left: Will the '66 housings go into a '67-'70 or '71-'73 car, or are their mounting points different?
  6. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    Thread is stuck!!!:beer
  7. Dale

    Dale Sweepspear


    Thanks David,
    Theres nothing like comparison photos to help make sense of things!
  8. DaWildcat

    DaWildcat Platinum Level Contributor

    Thank you VERY much for posting this info...you may well have saved me from more than one headache.

    By the way, if you ever get tired of the 3.42:1/posi I'd be more than glad to purchase the parts! It's precisely what I'm after for my '67 Wildcat.

    Thanks again,

  9. telriv

    telriv Founders Club Member

    The best question that hasn't been asked, will the ring gears fit the other type carriers??? Yes, they are all 9 3/8ths. Will older gears fit (up to '70) on '71-'75 carriers??? Yes, again, they are 9 3/8ths also. Can older gears be installed in newer ('71-'75) carriers??? Yes, with some minor modifications & using an older pinion seal. Some of the differences are ring gear bolts. Older are right hand threads, newer are left hand threads. Try swapping around gears only & not full carriers & more can & will be learned. 3.23 & down uses one carrier & 3.42 & up use another. The 3.23 carrier can be used with 3.42 gears with an approx. 1/4" spacer & longer ring gear bolts. Ed & I did this 3 years ago & proved to our satifaction it can be done. I believe he has finally done this on his '73??? Riv. GS by installing older 3.90's in his rear housing.
  10. oPh

    oPh Well-Known Member

    Good info!!!

    The burning question, & one that wil require disassembling a couple posi carriers...
    Can 30 spline posi side gears & spiders be swapped from a high ratio '67-70 9 3/8 posi carrier into '71+ low ratio 9 3/8 posi carrier, so later carrier can be used in earlier rear???

    Just wondering, as for last decade have been able to build my own low & mid ratio posi P series 8 7/8 carriers out of later MP series carriers, doing similiar deal.

  11. SpecialWagon65

    SpecialWagon65 Ted Nagel

    Tom, would the ring and pinion from a '65 3.23:1 work on a '65 3.08:1 posi carrier? I'm going to try it for my Riv. Thanks for the great information guys.
  12. telriv

    telriv Founders Club Member

  13. quicksabre

    quicksabre Well-Known Member

    I'm glad to help with this as I can. Alot of good questions have been asked about this rear lately. It gave me an excuse to pull my 67 Riv out of the storage building where it has been for the last ten years to finally start working on it. oPh, I have looked into side gear exchanging between the 67-70 and 71-75 posis enough to see that you would have to change the spider gears also. The teeth look very different. What I don't know how to get around is that the posi clutch packs are totally different, including how they mesh with the backside of the side gears. The earlier one is Eaton with the four rounded tabs that rest in steel holders, while the later one uses the clutches with the two big square tabs that engage directly with the case.
    As for ring/pinion gears between the two eras, I still have never had an earlier and a later set pulled at the same time to sit side by side. I would think the ring gear bolt thread rotation could be gotten around, but I thought there was a question about the overall pinion shaft length.
    One additional thing that I just learned is that the 70 Riviera rearend has a different driveshaft flange than the 67. The 70 seems much more like the what the 71-75 uses. To my surprise, these are totally interchangeable. So I'm just using the 67 flange with the 3.42 gearset.
    I'm going to go ahead and see how I like how the car runs with 3.42 gears. If it does drive me crazy, I'll certainly try to sell it within the board here before resorting to anything like evilbay.
    It took me two days to pull all of this because the first day was spent getting the car into a position to work under it and get just the posi. Then I went back for the whole rearend the next day because the shock mounts are ripped off of mine and because the 3.42 gear/posi should fit perfectly back into the housing that they originally came in. But they have a few more Riv GS cars there, although they are all buried even worse than this one was.
    If they would just let me take the bobcat back there........ I could check all of these so much more quickly.
  14. telriv

    telriv Founders Club Member

    Ring & pinions cannot be changed amongst one another they are always a matched set.
    Older pinions are longer in length (up to '70) but can be used in '71-'75 (& '76??) housings. A small amount of machining is required along with an older pinion seal & an older driveshaft flange.
    Most all driveshaft flanges are interchangeable.
  15. quicksabre

    quicksabre Well-Known Member

    Interesting, what must be machined?
  16. DaWildcat

    DaWildcat Platinum Level Contributor


    Thanks for the info, David. If the 3.42 setup ends up being too steep for you, please keep me in mind.

  17. BTail

    BTail Well-Known Member

    72 Rear in 69 LeSabre?

    All right, let me get this straight. I test fit the complete rear end from a 72 Electra in the back of my 69 LeSabre, and it appeared to fit, although I didn't really complete the installation. Both cars had 2 upper and 2 lower control arms. So, if the 72 rear (which included a posi) would have fit in the 69 LeSabre, than I could have used a lower ratio gearset (up to 3.90:1?) from a late 60s 9-3/8" rear end? This very topic really bogged down my drag race LeSabre project which fizzled out several years ago now when the roof of my garage collapsed on the poor car due to snow load. Now the car is junked :( and the posi is gone (Zach's got it), but the question still keeps me up at night.
  18. jamyers

    jamyers 2 gallons of fun


    As I understand post #9 above, the R&P gears should swap, unless you run into a left- or right-hand thread issue.

    How confident are you that the '72 rear end housing would go into your '69? The early-and-late generation axle housing swaps are one of the still unanswered questions on these. It'd be really nice to know that the '70 mounting points were the only odd ones, that'd open up the search for a lot of folks.
  19. BTail

    BTail Well-Known Member

    Man, that was a while ago, and I didn't document what I did in any way. I believe I had the rear end attached to the frame via the four links, but I don't recall how the springs or shocks would have worked out. I'm not really sure how well the upper control arms attached to the axle, but I believe I had it all bolted up. I also don't recall which control arms I was using for this trial fit, those from the 72 Electra or those from the 69 LeSabre. I wasn't really considering using the Electra rear end due to lack of available low ratio gears, but threw it in there just for grins. It also had a flanged driveshaft connection versus the original LeSabre 10 bolt's standard u-joint connection, but I was planning on running the Electra driveshaft, trans, and engine anyway. Hopefully, somebody else reading this can positively confirm or deny how the 71 and up 9-3/8" rear end would fit in a late 60's non-Riv full size Buick (69 LeSabre in my case), because I can't really state positively how well it would work. Sorry. Is it getting smoky in here, or is it just me?

  20. pontchief

    pontchief Norwegian car nut.

    My 76 Buick Electra is my first Buick ever, but for sure not the last one. :) I really love this car and I am really looking forward to get it back home to Norway. :3gears:

    But over here I really could need a posi rear end.
    In this tread you are talking about up to 70 and 71 to 75.

    What happens in 76 was there a new rear end, totally different from other years?

    Per Arne

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