Crazy Custom Hybrid Gearbox....

Discussion in 'Modifications And Maintenance' started by Chux, Dec 15, 2006.

  1. Chux
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    Chux Well-Known Member

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    So, ever since my EJ22/Rx trans swap, the only thing I've been very unhappy with is the gear ratios. This trans, despite the 3.70 final drive, turns about 3500 rpms at 75 mph. So I started doing some research...and found a guy using a forester 5th gear in an RX tranny....

    So, after trying to find what gear ratio a forester 5MT used for 5th gear...and having no luck....I've come up with a new plan.

    first, some gear ratios:

    Gen 1 Legacy, according to '92 FSM:
    FWD 5MT
    1: 3.545
    2: 1.947
    3: 1.366
    4: 0.972
    5: 0.738
    FD: 3.70

    AWD 5MT
    1: 3.545
    2: 1.947
    3: 1.366
    4: 0.972
    5: 0.783
    FD: 4.111

    EA82, according to '89 FSM:
    N/A D/R 5MT
    1st: 3.545
    2nd: 1.947
    3rd: 1.366
    4th: 0.972
    5th: 0.780
    Final Drive: 3.90
    Lo Range reduction: 1.592

    RX FT4WD 5MT (What I'm currently running)
    1st: 3.545
    2nd: 2.111
    3rd: 1.448
    4th: 1.088
    5th: 0.871
    Final Drive: 3.70
    Lo Range reduction: 1.196

    Now this is all assuming that some (if not all) EJ gearsets can be used in an EA trans.

    EA82 N/A or AWD Legacy 1-4 (same ratios, I'm leaning towards the Legacy ones...assuming they're stronger)
    FWD Legacy 5th
    EA82 N/A lo range
    RX center diff and final drive (Todd seems to think a Mazda 323 GTX viscous locking center diff could be used....I think he's got one...so I plan on finding out...)

    This would yeild:
    1: 3.545
    2: 1.947
    3: 1.366
    4: 0.972
    5: 0.738
    Final Drive: 3.70
    Lo range: 1.592

    which would mean, on stock tires (ignoring the fact that I'll probably be on bigger ones), this means that in 5th Hi, at 75, the engine would be turning a relaxed 2900 rpms.

    And, when lo range is engaged, it would be like having a final drive of 5.9:1. Which means, in 5th Lo, 5k rpms would be 78 mph. Which would work out perfect for even the fastest of courses.

    none of those calculations take into account the fact that I'll probably be on slightly larger diameter tires aswell...

    AND, still keep the locking center diff. While I have it all apart, I would really like to put in a front LSD. but that'll depend on the cashflow at the time


    I would also like to get the gearsets cryo treated....because if this goes well, I'll be pushing some big power through it before I move on :naughty:

    and the coolest part, is of all those parts, the only thing I don't have, is the FWD 5MT legacy 5th gear.....that'll be a little difficult to find...but beats the hell out of buying an STi 6MT. but gives me a greater spread of gear ratios!