K Frame Substitution Using For F Body Coupes

F Body General Discussion

  1. Bongy337

    Bongy337 New Member

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    After following several threads from Jeep forums regarding 8.25 rear axle with disc brakes setup that can work with old mopars, why not try the following to modernize these old cars and make them better. Well, I've actually come across another option that I like better. Something came up on my radar screen that REALLY got my attention. That is, the drop out IFS from a 93-04 Lexus SC300\400. It's a REAL nice looking piece and it's got a hair over 34" between the frame rails. Just like the F-body. It can use HUGE Turbo Supra front disc brakes and it bolts to the frame. F body front track width is listed as 60.0". SC300\400 is listed as 59.8"... Thinkin' out loud.... Haven't tried it but what are your thoughts?

    Lexus-SubFRAME.jpg
     
    Last edited: Jun 13, 2018
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  2. 89.Fifth

    89.Fifth Well-Known Member

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    I saw someone else trying this too. I think it's a great idea if you can get all the bits to line up!
     
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  3. MiradaMegacab

    MiradaMegacab Well-Known Member

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  4. Idle Ender

    Idle Ender Well-Known Member

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    Oh no. Dont plant dreams of 2J swaps in my head.

    Having done the 8.25 Jeep swap on my F-body, maybe Ill try this next. lol
     
    Last edited: Jun 18, 2018
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  5. Dr Lebaron

    Dr Lebaron Well-Known Member

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    If I was better at computers, I'd get a 3D scan of both K frames and check out the differences.
    The .2 track difference shouldn't be a issue
     
  6. Idle Ender

    Idle Ender Well-Known Member

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    Only thing Im worried about is suspension clearance.
     
  7. Bongy337

    Bongy337 New Member

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    Good job. How was the fitment with the JEEP axle? Could you provide some details as to the year used, etc... Thanks
     
  8. Idle Ender

    Idle Ender Well-Known Member

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    It was like an 04 or something. I wrote up a walkthrough on here a while back.

    Heres a link: Jeep Liberty 8 1/4 rear swap
     
  9. BudW

    BudW Moderator Staff Member

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    The axle shafts (Dodge calls them driveshafts) are the same for Left and Right sides for the 7¼” as well as the 8¼” (but different between the two different size differentials) FMJ differentials.
    They are also the same (for each side) for the rear differential on the 2002-2007 (KJ) Liberty’s – so the carrier offset will be the same.

    The Liberty’s came with the Chrysler design 8¼” differential as well as Dana 35. The Dana 35 has a 7¾” ring gear so my opinion is the Chrysler 8¼” version is stronger (but others might disagree with that).
    They come in drum brake and disk brake versions – with disk brakes are far more common.

    The width (where wheel attaches to drum/rotor) is 63-3/8”. FMJ vehicles are 59-3/8” drum to drum – which makes the wheel attachment point 2 inch (50 mm) wider per side.

    The Liberty’s do not use leaf springs – so the attachment brackets will need to be cut off of housing and new leaf spring perches welded back on. New perches are fairly easy to find.

    The axles also use 5x4.5” wheel bolt pattern (same as FMJ’s) so existing wheels should still work – providing there is no tire to chassis contact anywhere.

    Liberty differential ratio options are 3.73 and 4.10 (and maybe others?) and they come with or without limited slip. The ring and pinion gear set will interchange with most if not all Chrysler design 8¼” differentials.

    The carriers and axles have a different axle spline count than what FMJ vehicles use (27 vs, 29 spline, I think). Axles are a different width so no issue there – but to convert a Liberty axle to limited slip, you will need a ’97 or newer 8¼” or newer carrier.

    Liberty’s also use a different differential yoke. A person can either remove and reuse the yoke from your existing FMJ or convert to the newer style design.

    The data for the 2008-2012 (KK) Liberty’s has not been obtained – so not sure about them, yet.
    BudW