e36 diff ratios

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  1. e36 diff ratios 
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    Hi all, was wondering if someone could tell me the best way to go about getting better acceleration from an e36 325i via altering diff ratios?
     
     

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    i was going to ask the same question! i,ve heard that the "M3 lightweight" had a 3.23 diff ratio which helped acceleration, but finding one may be difficult, also it also an LSD.
     
     

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    i'd guess that as the 325i has a 3.15 as standard then 3.23 may not be a substantial gain.
    i was wondering if if something like the lsd from an e34 with a 3.64 ratio would fit or be made to fit?
    am i right in understanding that to be able to fit new gears into the diff housing it needs to be an e36 lsd to start with? i,e you can't fit new cogs into the non-lsd diff?
     
     

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    AS I understand it you have the medium sized diff case, and therefore being a smart company BMW use same sized cases across various models of a similar era.

    In my view LSD is sensible to find to keep the power being more effective, harder to find and pricey to build.

    As for ratio that depends on what you want to achieve and what other changes you have done.

    Std diff was 3.15, can't recall gear ratios of the box you have, but as a quick example:

    If 1st gear is 4.1 and second is 2.3.
    Wheels are 18inch 255/40
    and rev limit is 6700

    then you hit max speed in first 2 gears at ~40 and 71 mph, with a 3.15 diff
    the first to second gear change drops revs from 6700 to 3750ish.

    One theory is gear change from max power to max torque.

    If you are after 0-60 then 2nd gear change should be just after the 60 but this may not suit the engine power / toque curves.

    Now if we use a diff of 3.64 with same wheel and tranny then max speed is 34 and 62 respectively with similar rev change.

    Hope that helps a bit, several calculators around on web.
     
     

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    i'm not sure you will be able to hit 62mph in 2nd with a 3.64 diff. i mean, i have a 3.15 and i still am not able to hit 60mph in 2nd. i have 16"s tho'..
    There are only two products required to make the universe work properly: Duct tape and WD40. 


    If it moves (and it shouldn't): duct tape. 
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    Everything else is just stuff.
     
     

  9. alexdavi 
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    then what we need to do to hit 62mph in 2nd ?
    alex
     
     

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    Quote Originally Posted by alexdavi View Post
    then what we need to do to hit 62mph in 2nd ?
    i reckon a 2.93 diff. it depends on the gearbox's ratios as well, but a 2.93 should be able to hit 62 in 2nd, all day every day, but at some acceleration expense.
    Last edited by mistreku; 27-06-2010 at 18:30.
    There are only two products required to make the universe work properly: Duct tape and WD40. 


    If it moves (and it shouldn't): duct tape. 
If it doesn’t move (and it should): WD40.

    Everything else is just stuff.
     
     

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