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Thread: Identifying an 8.5" S-series rear end.

  1. #1
    Registered User ZZ4Blazer's Avatar
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    Identifying an 8.5" S-series rear end.

    Heres a few pictures I have taken of both my 8.5", and a 7.5" rear end out of a 2wd S-series.

    Here are the differences, and easiest ways to tell between the 2.


    As you should know, there are 2 main visual differences between the two.

    First, here is a 7.5" rear end. Notice how the axle tubes are straight, and how the rear end cover is more square.





    Close up of the axle tube.






    Now, heres a picture of the 8.5". Notice how the cover is almost completely round, and the bugle in the axle tube just before it goes into the pumpkin.




    Close up of the axle tube. Notice how the tube bulges right before it goes into the pumpkin.





    A shot comparing the 8.5" cover (left) and the 7.5" cover(right).






    Now, as I've said, most usually you'll have to have your driveshaft shortened going from a 7.5" to the 8.5" This picture should fully explain why. Looking at the flat surface where the cover would mount, notice how much taller the 8.5" is.




    Hopefully that should explain the visual differences between the 7.5 and the 8.5", and how to identify one.
    Last edited by ZZ4Blazer; 12-08-2004 at 01:41 AM.
    Jim 94 Stepside
    ZZ430 clone V8
    NX kit in the works
    Tremec T56 6 speed
    8.5" rear
    Quote Originally Posted by Harley
    Go before show any day of the week.

  2. #2
    Registered User Catching Second's Avatar
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    You're the man.
    "A true hotrodder wouldn't be content untill he had created a car so violent, so hairy, so totally sick that the very act of dropping the hammer would result in instant death. Anything less results in the need to go faster." - Tony DeFeo

  3. #3
    Fully Erect Member LowKat's Avatar
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    Thanks for Rearends 101

    Now I'm gonna be on the lookout
    Originally posted by Blazin Low:
    In 1972 a crack commando unit was sent to prison by a military court for a crime they didn't commit. These men promptly escaped from a maximum security stockade to the Los Angeles underground. Today, still wanted by the government, they survive as soldiers of fortune. If you have a problem, if no one else can help, and if you can find them, maybe you can hire Tony Low
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  4. #4
    built not bought pimpinblazer89's Avatar
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    pics dont work:(
    Jeff
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  5. #5
    Registered User ZZ4Blazer's Avatar
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    Somethings up with car domain. I had the same problem last night right after I posted them. I played with it for like 45 minutes trying to get them to show up, thinking I had something wrong with the link. Then, they just showed up and started working again.

    Be patient, Im sure they'll show up here in a little bit. If not, I'll change it around.
    Jim 94 Stepside
    ZZ430 clone V8
    NX kit in the works
    Tremec T56 6 speed
    8.5" rear
    Quote Originally Posted by Harley
    Go before show any day of the week.

  6. #6
    gas assassin slackware's Avatar
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    I think the quickest way to spot a 8.5 is the small tabs on the bottom. Notice how the 7.5s are points and the 8.5s are square?

    at least thats what I do
    85 sbc blazer

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    8.5" REAR DIFF FOR 2WD

    I have one sitting around if anyone is interested!
    11.03@122MPH

    www.lt4blazer.net

  8. #8
    Senior Member noob's Avatar
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    so what rear end do i need for an 86?

    ok, so i got an 86 s-10 and im looking for a posi rear with disk brakes, or at least disk brakes...
    ordred one from a 95 and it was wrong...but it wasnt even disk brakes, im pretty sure it was the 8.5"

    but waht rear end will fit the 86 and be the same length
    Thanks

  9. #9
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    Re: so what rear end do i need for an 86?

    Originally posted by noob
    ok, so i got an 86 s-10 and im looking for a posi rear with disk brakes, or at least disk brakes...
    ordred one from a 95 and it was wrong...but it wasnt even disk brakes, im pretty sure it was the 8.5"

    but waht rear end will fit the 86 and be the same length
    Thanks
    Not sure I understand. Did you actually by one from a 95? I don't think they came with disc brakes unless you happen to get one from a Blazer. All the ones I have seen were drum brakes. Most of us have converted to rear disc by using late model f-body disc brake setup! Tube size going in to housing is the thing that is the easiest to determine 8.5.
    11.03@122MPH

    www.lt4blazer.net

  10. #10
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    s10 rear width?

    This was great info on the differences between the 7.5 and 8.5 rear. A detail that I need for my project: I've heard that there are different widths depending on whether you have an s10 pickup or blazer and whether it's 2 or 4 wheel drive. I'm looking for something that is: 1. 60" from wheel mounting to wheel mounting. 2. 8.5 ring gear. 3. 3.73 posi. 4. disc brakes. I don't think the zr2 option will work as the measurement is too wide, but maybe you guys have other info?

  11. #11
    Registered User ZZ4Blazer's Avatar
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    I believe that stock 2wd rear end is 54" wide drum to drum.

    I also believe that stock 4wd is 58" drum to drum.

    Blazer, truck, doesnt matter, 2wd is 2wd. Only differences between the width is 2wd, 4wd, or the ZR2 rear end.

    I think your gonna be a little hard pressed to find an 8.5" that is exactly like your looking for. Would probably be easier to add posi and the gear ratio you want.
    Jim 94 Stepside
    ZZ430 clone V8
    NX kit in the works
    Tremec T56 6 speed
    8.5" rear
    Quote Originally Posted by Harley
    Go before show any day of the week.

  12. #12
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    Thanks for your input!

  13. #13
    Senior Member billp's Avatar
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    S10 8.5 Zr2 Rears Are , I Believe, 65" Long.
    84 xCab S-15. No longer ugly but still quick

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    It was really a nice experience to read out from here because all the posts are interesting to read out and conating very useful information for the readers as well.
    testking 642-901 and 70-450 preparation especially for 1z0-050 and 1z0-051.

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    Zombie Killer 6SpeedBlazer's Avatar
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    Quote Originally Posted by Benalex View Post
    It was really a nice experience to read out from here because all the posts are interesting to read out and conating very useful information for the readers as well.
    die spammer

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