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  1. #1

    Post 8.8 donors for 1979 Fairmont Sedan

    Hey everyone

    1. What year and model ford 8.8s are a direct fit for a 1979 Ford Fairmont Sedan?
    2. Are there any benefits with the 7.5 over the 8.8?

    What models and years of mustangs, explorers etc came with an 8.8 which is a direct bolt up to my '79 Fairmont sedan without any modifications?


    I had a bastard teeny tiny 6.something differential and not the 7.5 which was a shocking discovery when I went to install my 3.73 Yukon Duragrip LSD kit because I thought the car only came with either the 7.5 or 8.8 and I know it wasn't an 8.8 for sure...BUT rather than trying to source a 7.5 I'm going to try and sell the kit and upgrade to the 8.8 with all the bells and whistles including 31spline axles. I think the 86-93 Mustangs share the same 8.8 rear ends but can anyone confirm that?

    The plan is to buy an 86-93 8.8 housing on eBay

    https://www.ebay.com/itm/1986-1993-F...4AAOSwA3dYJhxS



    and rebuild it with this kit from LMR

    https://lmr.com/item/LRS-4204SDK-A/7...Axle-Kit-5-Lug



    Are there any additional parts I would need to fit to the housing?


    LMR have a note about brake fitment being ONLY for Turbo coupe brakes with an adapter or drum brakes...I like the Baer SS4 5lug brake kit with the 12" rotors

    https://www.cjponyparts.com/baer-bra...92/p/DBR172-V/

    but I'm not sure if they'll work on this version of 8.8, might give Baer a call about that but for now, I just wanted to confirm I'm heading in the right direction with these parts to make it a painless swap.

    Right now the diff is welded and is soooooo tiny but holding, but VERY unsafe under boost.

    Here's a video for attention:
    https://www.youtube.com/watch?v=zIjw...c#action=share

  2. #2

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    .....
    Last edited by clownyj; 02-16-2020 at 03:02 PM. Reason: delete

  3. #3

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    This is the original tag from my diff
    From this its a 6.7...with a 2.73 ratio

    Name:  Differential Tag.jpg
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    Last edited by clownyj; 02-16-2020 at 03:02 PM.

  4. #4

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    Well, that sure looks like a 7.5. I've never heard of a 6.7". Ford used little 8" rears before the 7.5s came out...they look like a little 9".

    You'll be fine with any foxbody drum brake rear. You can transplant your fairmont brakes lines to it easily.

  5. #5

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    Quote Originally Posted by 4eyedblind View Post
    Well, that sure looks like a 7.5. I've never heard of a 6.7". Ford used little 8" rears before the 7.5s came out...they look like a little 9".

    You'll be fine with any foxbody drum brake rear. You can transplant your fairmont brakes lines to it easily.
    I want to upgrade to discs in the back though

  6. #6

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    That's fine, any of the kits you reference above will fit the standard drum 8.8. You can fiddle around with SN95 rears and stuff but, they are wider by 3/4 a side so, problems....

  7. #7

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    I rolled my rear fenders to fit 9.5width rims on 275 tires so maybe the might not be as significant...worse case I cut the fenders and fit some aftermarket fenders to add some curves to the square girl...but are there any alternative 8.8s with direct fitment and the same overall length?

  8. #8
    FEP Supporter Broncojunkie's Avatar
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    I've never messed with the 94-04 rears, but it's my understanding that the 94-98 is the one you want. If you are worried about it being too wide, you can swap fox axles into it and you'll have a fox-width disc rear.

    The 94-98 used the same case but longer axles due to the abs tone rings, iirc. In order to use fox axles, you'll need to move the caliper bracket from outside to inside. You can either cut and re-weld or buy aftermarket brackets (I believe).

    I'm just going from memory here, but it's been a few years. I suggest new axles anyway. Forged axles are quite a bit stronger and they're not too expensive.
    79 Pace Car - 331, t5
    79 Cobra - working on 351w, t5
    86 coupe - rotbox roller
    86 coupe - working on 408w, c4
    88gt - 302 efi, t5

  9. #9

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    Quote Originally Posted by Broncojunkie View Post
    I've never messed with the 94-04 rears, but it's my understanding that the 94-98 is the one you want. If you are worried about it being too wide, you can swap fox axles into it and you'll have a fox-width disc rear.

    The 94-98 used the same case but longer axles due to the abs tone rings, iirc. In order to use fox axles, you'll need to move the caliper bracket from outside to inside. You can either cut and re-weld or buy aftermarket brackets (I believe).

    I'm just going from memory here, but it's been a few years. I suggest new axles anyway. Forged axles are quite a bit stronger and they're not too expensive.
    How about the 86-93 mustangs?

  10. #10
    FEP Supporter Broncojunkie's Avatar
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    Quote Originally Posted by clownyj View Post
    How about the 86-93 mustangs?
    86-93 rear end was same case as the 94-98, but with shorter axles and drum brakes. They should be a direct swap for your Fairmont. If you want disc brakes, just buy the caliper brackets and do the swap. Honestly, though...if you plan on doing disc brakes, I believe scoring everything from a 94-98 is your most cost effective option. If you have clearance problems, do the caliper flip/fox axle swap on it and you're gtg.
    79 Pace Car - 331, t5
    79 Cobra - working on 351w, t5
    86 coupe - rotbox roller
    86 coupe - working on 408w, c4
    88gt - 302 efi, t5

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