Electra 75 rear end ?

Discussion in 'Got gears?' started by ghrp, Aug 18, 2020.

  1. ghrp

    ghrp Well-Known Member

    Hi guys,

    I was ready to swap my gears on my 75' Electra today but it seems that I didn't order the right ones. The differential carrier was junk as well so I'll need to replace it. It looks like a GM 8.5 but the axles had 31 splines on them.

    Could you guys link me a new carrier for my application, as well as the 3.42 gears I am looking for ?

  2. Luxus

    Luxus Gold Level Contributor

    Post a picture of the axle with cover, a couple of our resident axle experts will ID it for you. You may have what I have, a 8.875 Pontiac. There's also an Olds 9.3 that's found under a lot of Rivs.
  3. ghrp

    ghrp Well-Known Member

    From what I saw/measured, it really seems like it is a 8.75 w/ 31 splines. The cover is exactly like a 8.75 10 bolts.
  4. flynbuick

    flynbuick Guest

  5. ghrp

    ghrp Well-Known Member

    Just carefully read Luxus' thread about his rear end investigation. It turns out my inner bearing pinion measures 1.875, so my rear end is most definitely a 8.875. So frankly, my best bet is to look up for any used part ?
  6. Luxus

    Luxus Gold Level Contributor

    Welcome to the club! Good news it's a fairly stout rear end. Bad news is there is zero aftermarket support for it. So yes, used only.

    This is the place where I got my used 3.08 upgrade (over the original 2.73):


    There's a guy that has made a new 3.55 upgrade for our rears. He's out of stock right now but claims he will do another run soon. If your interested, call him and add your name to the list. It's a bit pricey, but we don't have much choice here.

  7. ghrp

    ghrp Well-Known Member

    Yup I did find both of those links on your thread :)

    The fact that there isn't any repro is a bit bumming, it'll put a damper in the schedule... but hey we can't help it!
  8. ghrp

    ghrp Well-Known Member

    Just spoke to Dave at Fabcraft and he said the 3.55 gears should be there around mid 2021... well !
  9. Luxus

    Luxus Gold Level Contributor

    Well that sucks. When I last spoke to him, he was thinking maybe this September. Well it is what it is.
  10. monzaz

    monzaz Jim

    <<<<<<<<<<<<<< Garbage is ment for the website NOT your post....:) just to clear that up.

    That wizard crap site is garbage for cars. Do not bother.
    Your looking at the wrong 8.875
    It is a Pontiac 8.875 or which I doubt is a 8.75 c-clip rear. 31 spline which came in mostly A-bodys in that era...
    So see if is is bolt in axles or c-clip axles.
    If it is a 8.75 your doomed
    If it is a 8.875 Fabcraft will have the one 3.55 set...IF they make it.

    PINION DIAMETER is the difference.
    8.75 has a 1.625 pinion diameter
    8.875 will have the 1.875 pinion diameter like the older 1965-1970 version (but will be 28 spline yoke) Where as the 1971 -1976 version is 30 spline .

    So really either or your in for the hunt of your life to get any kind of performance parts.
    Easier to just find a 10 bolt 8.5 out of a lower HP full size 1971 -1976 fill size car and install that into your Electra.
    You can get all the posi units and gears and bearings you want and they are up gradable to 30 spline if you can afford to purchase bolt in axles.

    JD Race
  11. Luxus

    Luxus Gold Level Contributor

    So Jim that 8.5 out of a full size car, would that be a direct bolt in? Or would it involve modifications to the mounting points (welding)?
  12. monzaz

    monzaz Jim

    1971 -1976 are all direct bolt in rears to each other...Hence the CORPORATE era of GM... ALL the A bodys 73 - 77 interchange with each other weather they are bolt in axle or c-clip axle
    Then GM in 1978 -1987 all BBody rears were the 73-77 Abody rears...Except for the Wagons... lol. Everything shrank. also.
  13. ghrp

    ghrp Well-Known Member

    Cool, then it is just a matter of properly reseraching...

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