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E34 5-Speed Swap

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    E34 5-Speed Swap

    Hi guys,
    I'm getting mentally prepared to swap out an automatic transmission for a manual 5 speed. Car is a 91 E34, tranny is ZF4HP22 and 5er would be from an 89 525.
    My question is about keeping my driveshaft and differential. Can I keep them? Or must they be replaced by units made for the manual box?
    Thanks
    Last edited by Rockabilly_Rebel; 07-18-2018, 05:26 AM.

    #2
    The diff should be fine but it will have a ratio that may be a little high for your expectations. You may want to go with something like a 3.55 or better. The driveshaft will probably be a different length though. Not sure on an e34. I just swapped a manual into an 88 6 from an 85 six. Used the 85 manual cars driveshaft. Good luck!
    sigpic

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      #3
      Yes driveshaft length will likely be an issue. But once you swap the driveshaft you may likely have to swap the diff too - the flange sizes where the driveshaft connects to the diff appears to be a different diameter between auto/manual cars and they may not be interchangeable.

      Auto to manual length side by side- the manual is tiny! (This is a ZF from an early e34). I would recommend trying to source the complete setup from a manual car. Even if for some reason the diffs will swap, the ratios may not jive. The ZF trans has a 1:1 5th gear ratio - there is no overdrive like the auto has, so a numerically lower rear diff ratio is normally preferable. Depends on what your tolerance is for your rev counter and highway speeds

      -Geno

      '87 325is (s52'd)
      '95 525iT
      '02 Range Rover 4.6 HSE

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        #4
        Thanks for the info guys.

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