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Thread: Differential Rebuild or buy new?

  1. #1
    Join Date
    Oct 2002
    Location
    Cincinnati
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    130

    Differential Rebuild or buy new?

    I just got a 99 cobra diff. and I was debaiting if I should just rebuild mine or go with a fard racing or an auburn Pro. I have about 102k on my 95 engine rebuild less than 2k ago and thats really the only thing I need to replace, So I figured Since its going to be out anyway

    Once Dave D. Finishes my heads ill be in the range of 350 rwhp

  2. #2
    Join Date
    Apr 2002
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    St. Charles, MO
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    Do you have the whole Cobra pumpkin or just the diff ?

    David
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  3. #3
    Join Date
    Oct 2002
    Location
    Cincinnati
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    130
    Just the alum diff but I might still be able to get a hold of the internals but I did not think that would work? I know the 99 have 28 splines but I thought something was differant?

  4. #4
    Join Date
    Apr 2002
    Location
    St. Charles, MO
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    21,137
    I'm not sure I understand what your trying to accomplish. What are you planning to do with the empty Cobra diff case ? Did you get the aluminum case just to save some weight...are you planning to transfer all the internal parts from your existing pumpkin ?

    Is the diff you have in the car now a traction loc ? Are you installing gears ?

    David
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  5. #5
    Join Date
    Aug 2004
    Location
    Batavia,OH
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    2,019
    I have all of the tools to rebuild these diff correctly and the know how to make them last. I can add an extra friction to a stock TL carrier as well.
    Alan

  6. #6
    Join Date
    Oct 2002
    Location
    Cincinnati
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    Im sorry dave its just me not explainging I got the empty diff to save weight but since its out and I have 100k on mine I thought it would be nice to beef it up a little. I have the stock 95 rear with the exception I do i have 3.27 gears but thats it everything else inside is stock and never been replaced. Just kind of hoping to get opinions on if its worth it to beef up with the FMR, auburn pro or just rebuilt the stock.

  7. #7
    Join Date
    Apr 2002
    Location
    SW Michigan
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    2,222

    Detroit Tru-Trac

    You mention that you have a stock 95 rear end (differential). You don't say if you have a Trac-Loc or Open diff. Both were "stock" in '95.

    With the kind of hp/TQ that you'll have, you should probably go with something stronger than a Trac-Loc, in your new alum. case. If you do in fact have a Trac-Loc & want to keep/rebuild it, the alt. stacking method looks like it will handle more TQ than the Ford stacking method.

    I will never recommend a Regular Auburn Cone, which I have. I can feel it slip about 1.5 revolutions before it grabes. The Auburn PRO has more bias pressure that the regular, & is more suited for SC's.

    When I replace my Auburn Cone, It'll be with a Detroit Tru-Trac. The Tru-Trac is a Worm/Wheel design (clutchless). Allows full differentialization around corners, but locks solid when you race. It's suppose to handle at least 500 hp!!!!!

    The OEM 8.8" Trac-Loc in SC's is a Medium Duty unit. I tore up 2 of'em (both with 30K mi. on them), before I put the (regular) Auburn Cone in.

    68COUGAR
    Last edited by 68COUGAR; 05-30-2006 at 10:29 PM.

  8. #8
    Join Date
    Apr 2002
    Location
    St. Charles, MO
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    21,137
    I think your in for a ton of work for very little weight savings. If the pumpkin you already have is a trac loc which I assume it is, I think your better off rebuilding the clutch packs using the alternate stacking method and larger "S" spring that Mark mentioned.

    If you swap housings then you have to do a bunch of other stuff to get the correct preload and gear enguagement/backlash ect...ect....

    David

    PS: I'm using the stock trac loc in my 91, and I have an Auburn Pro in the 93 and both feel the same to me.
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  9. #9
    Join Date
    May 2002
    Location
    NYC
    Posts
    17,432
    If your car has the traction control button (auto) it isnt traction loc and you would need a whole new differential. The 99 cobra internals all work fine.

    As Alan has said you can rebuild the diff (if it sa traclock ) with more disks and a tighter spring for even better performance.

    So #1 do you even have a posi?
    #2 If no get those stock 99 cobra internals
    #3 Get it rebuilt..Might as well
    #4 No need for an Auburn

    I wouldnt even bother however just swapping everything from yoru iron carrier to teh aluminum..Get the aluminum one done then install complete,,Swap in swap out

    Just my two cents
    They don't call me "SLOWPOKE" for nothin!
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