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  1. #1

    Default Will a 31 spline carrier from 2013 GT work?

    I am getting close gathering all the parts for a 8.8 swap in my '85 T-top. I came across a 31 spline carrier out of a low mileage '13 GT with 3.73 gears for $125. To my knowledge these are the same carrier used in '03-'04 Cobras, so it comes with carbon fiber clutch plates and should stand up to some power. Would this work in the '89 8.8 I am building to swap into my '85? I need to order fox length five lug axles anyways... so should I stick with the stock 28 spline unit or upgrade to the 31 spline? Thanks for your input!

  2. #2
    Moderator wraithracing's Avatar
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    The carrier will swap into your 8.8 housing. Assuming the '13 GT differential is in good shape and the price is right then it could be a great buy.

    Depending on your expected power level will determine if the upgrade to 31 splines is necessary. Never a bad idea, but if your power level is relatively low then there is no real benefit to the upgrade. Good Luck!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  3. #3

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    Thanks Trey! Right now the motor is stock, aside from a Weiand intake and MSD ignition. I know a 31 spline is overkill at this point, but someday down the road I want to build either a street friendly 351 or go down the rabbit hole doing a Coyote swap.

  4. #4
    FEP Super Member erratic50's Avatar
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    Some thoughts along that line.....

    Personally I've never seen less than 500 HP tear up 28's. It is a bit of a toss up though.

    I've heard of people with 400HP/torque and drag race worthy suspension and sticky tires with 4.56's twist stock axles.

    Different ratios multiply force at vastly different rates. Also stored energy and traction conditions make a huge difference.

    Lots and lots of variables here...

    What does the car weigh?

    whats the mass of the unsprung weight in the rear?

    Is it a 40 lb clutch/pressureplate/flywheel package or only 20 lbs of stored centrifugal force beating on it?

    Is the 1st gear 4:1 or 2.95 or less :1?

    On a given launch, will the car dead hook?

    Does it slip the tires but just not enough to go up in smoke? Etc

    At a certain point things like 31 spline axles and c-clip eliminators become cheap insurance. A broken axle upon tire shake right after running a 1.3 (or even 1. 60 foot is likely to be a major wreck.

    Sometimes better 28's is more than enough.

    Sometimes guys are lucky too. Look closely at beater bomb sometime. (Those look like stock 4 lug axles)

    I'm putting 28 spline fox length Mosier axles in my 86GT. I'll run it with a 3.90 rear gear and 2.95:1 low and a 25lb clutch/flywheel package and around 400HP. Likely a 315/35/17 drag radial.

    Good luck on your mods.

  5. #5

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    If your are serious in your goal of more and more HP into the future, you're smart in your thinking. I learned early on about building a car backwards. The more HP you add, the more parts break. Starting with a good rear end , driveshaft , tranny and clutch, you can increase power levels without the fear of finding the weakest link.
    84 Cougar, 90 HO with 700DP, Edelbrock RPM intake, 1.7 RRs, shorty's and SS exh, T-5, KC clutch, Hurst pro billet, line loc, 8.8, 4.10s, suspension mods....blah, blah,blah.

    71 Comet, 289, Liberty TL, 9", 6.00s, 11.9x @ 112.... blah, blah, blah.

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