What rear do I have?

Discussion in 'Got gears?' started by Luxus, Feb 18, 2020.

  1. Luxus

    Luxus Gold Level Contributor

    I have a 74 Buick Lesabre w 455. I'm trying to positively identify what rear end it has. From other threads here it should be a 8.5 or a 9 3/8. But looking at it, it looks like a 8.2 B.O.P???

    Rear end small.jpg

    Can anyone help me ID it?
     
  2. johnriv67

    johnriv67 Well-Known Member

    Doesn’t look like a 9 3/8
     
  3. DasRottweiler

    DasRottweiler -BuickAddict-

    Looks like it has original "posi tag" on it....JIM
     
  4. flynbuick

    flynbuick Super Moderator Staff Member

    If the 455 is original to the car, another rear used about that time was a 8.875. Ask Brian or Monzaz.
     
  5. Luxus

    Luxus Gold Level Contributor

    I checked with monzaz and he thinks it's probably a 8.75 or possibly an 8.875. The only way to know for sure is to take it apart and measure the inner pinion bearing size.

    I asked the question because I want to upgrade the gears over the 2.73 that is in there now. I have to figure out if the aftermarket supports either of those two rears. The impression I get is those rears are kind of rare.
     
  6. monzaz

    monzaz Jim

    WOW thought a wrote a whole deal on this earlier today...I guess it was deleted and or never saved after I wrote it. Crap.

    8.875 or 8.75
     
  7. monzaz

    monzaz Jim

    8.875 or 8.75

    Usually with the fill plug it is a 8.75 BUT covers for the full size cars are interchangeable.
    SO you need to measure the pinion inner bearing size to determine what you have.
    1.875 the rear is a 8.875
    or
    1.625 shaft size will be a 8.75.
    Both came in 31 spline and the 8.75 was also 28 spline axles too.


    LOL. He sent this to me in a PM...That is where I answered it.... :) Thought I was going crazy...
     
  8. Bens99gtp

    Bens99gtp Well-Known Member

    Jim going crazy????? Haha, are we not all a little crazy????? I know I am!!!!!
     
  9. Luxus

    Luxus Gold Level Contributor

    Yea, I reached out to you in PM because I wasn't sure you would see the thread. Sorry for causing any confusion.
     
  10. monzaz

    monzaz Jim

    lol...No biggie. :)
     
  11. Luxus

    Luxus Gold Level Contributor

    So my research indicates that if I got an 8.875, I have options on ring and pinion. If I got an 8.75, I'm screwed.

    I may wind up taking apart my rear just to find out what I got (please, please 8.875).
     
  12. Bigpig455

    Bigpig455 Fastest of the slow....

    Looks like an 8.875 to me, just did mine on my 72 G-Ville. Monza's has undoubtedly filled you in on carrier breaks. Pontiacs are a great source for 3.08's
     
  13. monzaz

    monzaz Jim

    YES.
     
  14. Luxus

    Luxus Gold Level Contributor

    Noob question here. When you say measure the inner pinion bearing size, what specifically are you referring to? Looks like the pinion has two bearings. Is is the pinion diameter underneath the bearing? The one closer to the front of the car or the one closer to the back?
     
  15. monzaz

    monzaz Jim

    tHE INNER PINION BEARING IS THE ONE that is the big one IN the rear
    the Outer pinion bearing is the one most OUT of the housing. :)
    Jim
    JD Race
     
  16. Luxus

    Luxus Gold Level Contributor

    OK, got it all apart. The bigger bearing is still attached to the pinion. So that's the one I need to check. But of course I forgot my verneer caliper at work. So I got some thin wire and wrapped it around the shaft once where the bearing sits and the circumference is about 6 inches. That works out to about 1.9 or the 1.875 shaft diameter.

    I will double check the measurement tomorrow with more accurate measuring tools but it's looking good.

    BTW there is a number stamped on the pinion:

    41-15 GM J 73 A H2

    Dont know if that means anything to anyone as far as confirming what rear I have.
     
  17. monzaz

    monzaz Jim

    1.875 is the 8.875 rear. also 9.3 olds rear.
     
  18. monzaz

    monzaz Jim

    1.625 is a 8.75 rear has the same size pinion as the 8.5 rear just bigger ring and 12 bolts on the ring. basically a degraded 8.875 pontiac rear. mostly came in 28 axle spline versions
     
  19. Bigpig455

    Bigpig455 Fastest of the slow....

    Luxus likes this.
  20. Luxus

    Luxus Gold Level Contributor

    I did a proper measurement and the shaft diameter is 1.874, which confirms it is an 8.875.

    I've been reading up on the 8.875 and I don't have THE 8.875 rear (which would be a Chevy car or truck one and has tons of aftermarket support). I have a Pontiac one and that probably means the internals are not interchangeable between the two. Rhett thanks for the lead on the 3.08. I assume that means there are no vendors which support this rear.
     

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