Replacement rear 3.42 diff for 4x4. Can I mix ratios?

Discussion in 'General Discussion' started by hoes-before-bros, Aug 12, 2019.

  1. hoes-before-bros

    hoes-before-bros TYF Newbie

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    I have a 97 Burb 5.7L K1500. It has a factory 3.42 gu6 g80 diff on the front and rear.
    My rear has rusted through the horizontal pipes, is leaking and I need to replace the entire read end.
    The only rear ends I see on craiglist are 3.73 gt4 g80.
    is this an option?
    Will the gt4 fit seamlessly?
    Can i damage my vehicle if I use 4wd with diff ratios?
     
  2. SUBURBIAN

    SUBURBIAN All GM

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    Do not run two different gear ratios in 4WD. Either find a GU6 rear end, or swap both the front and rear for GT4's. You can run the GT4 rear and leave in the GU6 front, with the front driveshaft removed, until you can get a GT4 front, but then you will have no 4WD until the front is swapped to match the rear.
     
  3. hoes-before-bros

    hoes-before-bros TYF Newbie

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    Thanks. Would you know if a gt4 will fit with no modifications?
     
  4. R3cord303

    R3cord303 American Capitalist

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    Your gauge cluster will be lying to you is the other issue. Odometer and Speedometer will be wrong. If you put it in 4wd with the missmatched ratios you're going to break a bunch of stuff. If you do both front and rear differentials to GT4, then your only problems will be the odometer and the speedometer.

    If you're talking an entire rear axle swap to one that had the GT4, you may have issues with ABS stuff or brake lines being different but I don't know anything specific about this generation. I just know what sometimes things change mid gen.
     
  5. SUBURBIAN

    SUBURBIAN All GM

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    Speedometer & odometer calibration can be adjusted through the truck's computer.
     
  6. liquify33

    liquify33 Member

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    Mine has 3.73’s stock so that shouldn’t be an issue, IMO so long as you change both or disconnect front as mentioned above.
    I would think the housings are the same
     
  7. avalonandl

    avalonandl Full Access Member

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    A good shop can swap in your ring and pinion. Any good rear end from the same year should swap in as long as its the same pumpkin size.
     

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