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Thread: LSD final ratio changing.... can it, and how is it done

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    Senior Member dave2221's Avatar
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    Default LSD final ratio changing.... can it, and how is it done


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    ooookay

    so here is my dilema, my hachi is a daily, and as such i drive down from syd to uni 4 times a week.

    if i was to get a 4.6 final on a 2way LSD that would put cruising speed 110km/h at about 4500rpm.....
    NOT PRACTICAL

    i want a LSD, but can i get one with a lower final, (around stock of 3.7) and then at the end of the year can i just change the final out for something more drift friendly? to something like a 4.3 - 4.5

    or do i have to change the whole centre, and get a new 2way with the right ratio?

    thanks

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    You're only changing the crown and pinion, not the LSD (centre) but you will need to set it correctly otherwise the diff will whine and wear. I would recommend taking it to a diff shop to set up.

    You may be better off getting two carriers, and set one up with your LSD and fully sik drift ratio and another with a cheap open centre and more highway friendly gearing. If you've got a zenki rear end you could get a spare carrier off an old celica.

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    Senior Member aaron's Avatar
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    ive got 2-way and 4.1 in my daily.
    i drive to uni four or so days a week (short run down the freeway)
    i think it pulls about 3400rpm at 100kph which is ok. i wouldnt mind going to 4.3 bit more fun on the street

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    http://users.tpg.com.au/users/loats/...gearboxes.html - ratios

    http://www.miata.net/garage/tirecalc.html - roll out

    check your maths. pretty sure youre a fair way out.

    remember stock adm is 3.9 (not 3.7), but thats irrelevant, stock jdm is 4.3. 4.6 is not a big jump.

    i run 4.8 and its no big deal. highway cruise is over 4k but not much.

    adm and jdm t50 have the same ratios.
    78's

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    Veteran slydar's Avatar
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    also yeah, you just swap the raing and pinion, or, more likely, just take the lsd mech out of the lower (better ) ratio carrier and put it in the taller one.

    that way you dont have to set up the pinion again, which is the tricky part. changing the center can be done at home, you kinda need a rattle gun but apart from that you can do it by touch, dont really need the dial gauge/paint.
    78's

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    Slydar, you might have saved me some cash .

    ok so i got a 2 centres . both zenki . one with a trd 2way with a broken 3.9 final ratio and the other from a celica with a welded +4.1 final ratio. so i can just take the 2way lsd centre out and re-install into the 4.1 without setting up the the pinion ??????

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    Veteran slydar's Avatar
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    yeah, its fairly easy to set the back lash. just have a feel of the bearing tensions and back lash before you pull it apart, and then set it up the same.
    78's

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    well in that case i might get a 2 way with a 4.5 final (or there abouts)

    and just use the stock final while i am going to uni.

    i got 30 mins each way on the freeway and with the current ratio it sits at 3300 or there abouts which means its pretty good on exhaust noise so its comfortable to drive.

    thanks for the advice.

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    I have a 4.7
    does 80km @ 3,500 rpm
    the speedo is exactly 20km out.

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