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Thread: Rear end swap

  1. #1

    Default Rear end swap

    I have spent some time researching but have not gained the kind of understanding that gets through my thick skull. My car (85 conv.. converted to a V8 ) is running 4.11 gears in a transplanted 8.8 rear end. I have questioned all of the old hardcore gear heads around me, which is an admittedly small group as I live in rural Georgia. Everyone is telling me that the only people that they would trust to swap out a ring and pinion are either way way way too expensive, dead, or drunk and retired. That my best bet is to swap out the whole pumpkin with one that has the ratio that I want... 3.08 gears.
    I am pretty sure I can find someone to trade with me or to work out a deal with, but I have no knowledge whatsoever of rear end applications by vehicle.
    What kind of a rear end am I looking for? That is to say out of a pickup, out of a Mustang, out of an explorer, etc... in regards to the input and output areas.
    It is something that I have never had to learn thus far. I don't know enough to make a post about what im looking for.
    Educate me?
    Last edited by Toid; 02-17-2017 at 10:29 AM.

  2. #2

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    What do you mean exactly by "swap out the whole pumpkin"? Do you mean swap the entire rear end out? That would certainly work but wouldn't be the smartest use of your time. And that also assumes whatever is in the new rear was done properly and is in good condition.
    If you mean swap out the whole differential (traction lock and gears) that is no help at all. That is what you "set up" when changing gears, at least one of the most important things you set up. The differential has to be shimmed in the axle housing and that is the most important of all. It keeps the gears from being burned up in 50 miles so swapping a differential is of absolutely no value at all.
    So assuming you mean the entire rear, the only "bolt in" units that are OEM that work are 1986-1993 5.0 Mustang and Capri. There was an 8.8 in the 1987-88 Fox Thunderbird, and Cougar (not all versions had the 8.8 ) that works and bolts in but the axles are longer, thereby moving the wheels further out from the fenders. So it would totally depend on your wheels whether that works or not. You would also gain rear disk brakes with that unit but then that opens a whole other can of worms trying to get all that working. The Lincoln Mark VII also had an 8.8 with disk brakes.
    Last edited by homer302; 02-17-2017 at 11:11 AM.

  3. #3
    FEP Super Member bwguardian's Avatar
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    I think what you are describing as changing out the pumpkin is how the old Ford 9" works. The third member separates from the housing and includes the ring & pinion gears and the driveshaft yoke. The Ford 8.8" is different and more like the typical rear end unit in that you have to set up the ring & pinion...or change out the whole rear end...
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  4. #4

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    Quote Originally Posted by bwguardian View Post
    I think what you are describing as changing out the pumpkin is how the old Ford 9" works. The third member separates from the housing and includes the ring & pinion gears and the driveshaft yoke. The Ford 8.8" is different and more like the typical rear end unit in that you have to set up the ring & pinion...or change out the whole rear end...
    AHHH!! Bingo, we have a winner. I bet you are correct. As stated above, the 8.8 does not work like this. bwguardian for the win!

  5. #5

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    So I really need to find a good man and just replace my ring and pinion...

  6. #6

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    If you want to drive 6 hours each way I know a good guy, LOL!

  7. #7

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    I got a guy who knows a guy... Who lives near a guy, nearby me. Races a lot of Foxes... It's likely he's got one (or five)... PLUS he likely wants mine.

  8. #8

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    Too bad you are a long ways away. I have a 3.08 rearend and I want 4.10's.

    There has to be someone in your area in a similar situation. Or you can get the tag numbers for 3.08 rearends and find one in the local boneyard the sell your rearend with 4.10's. You'll get about double for it with those gears in it and ready to rock. Especially if you let them ride in your car and verify its good before you pull it.

  9. #9

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    I'm barking up that tree as we speak!

  10. #10

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    Good luck!

  11. #11

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    Just about an 86-93 gt has either 2.73 or 3.08 ratios from the factory. Little trick here, even the 94-04 mustang axles would swap right over, just reuse your axles and brakes/brackets to keep it te same width and 4 lug, the sell the 4.11 and 5 lug setup for profit.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  12. #12

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    Afaik there were more automatics with 3.08 than manuals but far more of both had 2.73:1.

    Totally not the end of the world if you a less steep street able factory ratio.

    2.73 * 3.35 (WCT5 1st gear) = 9.1455
    3.08 * 3.35 = 10.318
    4.10 * 3.35 = 13.735

    2.73 vs 3.08 is not a very significant change compared to the vast change going from 4.10 to either of these.

    Now for overdrive
    2.73 * 0.68 = 1.8564
    3.08 * 0.68 = 2.0944
    4.10 * 0.68 = 2.788

    Not a particularly big deal.

    Some of the SN95s had 3.27:1 rear gear available. Also not all that significantly different than a 3.08:1. Different yes, just not as dramatic as say 4.10.

    All of this said, what ratio you really want depends upon how fast you need to drive typically and how your motor is cammed. lord knows with proper maintenance you'll struggle to ever wear out a forged internals EFI 5.0L with 0.68 and a 2.73. I've beat the crap out of mine over a good long while plus two full seasons on the drag strip and after 440K+ it's finally showing its age damn the dry nitrous kit I put to it as that made it first start using a drop of oil finally at over 200K over 20 years ago

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