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Discussion Starter #1
I'm thinking of swapping out the rear axle on my 78 bird. I want to put in an axle off an early 90's bird or cougar. I was wondering if they would interchange with each other and what kind of gear ratio to use. I want to keep the fuel milage and yet have power. The car has a 3.8 V6 with a little over 100 thousand. Any help would be appreciated.
 

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why would you want to replace a 9 inch with a 8.8?
 

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jk89cat said:
why would you want to replace a 9 inch with a 8.8?
I think he mistyped and wants to put the 8.8 out of his MN12 into his fox 87 T-bird. If that's the case, it won't work as the MN12 has independant rear suspension and the fox body has a solid axle. You can use the gears out of the MN12 if the fox has an 8.8 in it but I think most of them came with 7.5 rears.
 

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yeah i was pretty sure 78's had solid axels. just figure out what gear ratio you have in your t-bird right now, and decide on what you want. if you just want power with still decent highway mileage 3.57s aren't bad. just depends on what future mods you want to do. i would recommend that you keep your current diff, and just swap the gears and replace the bearings.
 

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78 tbird

Hello

If the 78 has a 9" the gear would be 3.50 or 3.70. most likely can with 2.78
I had a couple of them. Along with Torino's.
If you can make & weld brackets you could adapt it to the IRS. alot of work.

PAUL
 

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Discussion Starter #6
It was a miss type i have an 87 not 78 that is my fault, but i wanted to know if the independent would be a good choice for it or not.
 

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racecougar said:
It would require quite a bit of fabrication to install the IRS into your 87.

-Rod
Not only would it require fabrication just to bolt it in, but cars with IRS from the factory are built differently than cars with a solid axle. For example, if you took the IRS out of a Cobra Mustang and tried to put it in a GT, it would be very unsafe.
 

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87 irs

Hello

I Agree, I beleave it would be un safe. Why change to the IRS Anyway??
Unless racing on a circle track there is no real advantage.
Also most FOX Mustang items will fit your car.

Any upgrade with solid axle would be the Quad shock on the rear end, like I have on my 85 coupe.

PAUL
 
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