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Changing final gear/drive ratio

Discussion in 'Engine Compartment' started by Sat-Chit-ananda, Oct 25, 2012.

  1. nkrishnap

    nkrishnap Staff Member Janitor

    Messages:
    1,900
    Bangalore
    Bangalore
    Linea 1.3
    The question is who will do it as the same spec as the OE one with very much the same finish and few quantities (say may be 10 pieces for experiement).

    It can be done, but definitely be a very tough task.
  2. I know a mechanic who does it,will update after talking to him.
  3. theblack

    theblack Esperto

    Messages:
    2,188
    Bangalore
    here are my concerns..
    Having a shorter ratio is going to cause nightmares in the city (as posted by you only from the wiki). That be the case why is there a need for this extra investment (money/time/man power) when highway driving is probably going to be only 20% of the actual driving experience.
    (Perhaps even less).
    Even in my wildest guess this entire change is not going to cost you anything less than 40-45k.(might be even more)
    And i feel that's not money well spent.
  4. Italia-Linea

    Italia-Linea Staff Member Janitor

    Messages:
    2,123
    Pune
    You need to find a gear manufacturing company. There are hell lots of them in India. Many vendors provide gears for oem companies like TATA Ashok leyland etc. They have gear hobbing machines. You need to provide them correct dimensions. They can cut the teeth for you.

    @ The black - shorter gear ratios enable quick pick up. taller more top speeds.
    1 person likes this.
  5. Here is the speed possible with 5th gear ration of .614, I calculated the differential ratio by the RPM and corresponding speeds achieved. Source http://www.kabamus.com/garage/gears.html
    gear_speed.JPG

    With Current .744
    gear_speed1.JPG

    - - - Merged Post - - -

    Punto is having shorter ratio.
    Last edited: Oct 30, 2012
  6. nkrishnap

    nkrishnap Staff Member Janitor

    Messages:
    1,900
    Bangalore
    Bangalore
    Linea 1.3
    ^^^ the above calculations are somehow off track. Because the current speed for 1000 rpm in 5th gear is 40 kmph.

    i.e

    1000 - 40 kmph
    2000 - 80 kmph
    3000 - 120 kmph
    4000 - 160 kmph

    Also the Punto tyre spec is 195/60 R 15 which will further reduce the speed. Please check the primary reduction and final drive to get the numbers right.

    Does anybody have the right secodary/axle drive ratio and the primary reduction. We can then manual play around with the ratios to see the gain or loss in revs for a given speed when the ratios are altered
    Last edited: Oct 30, 2012
  7. PatchyBoy

    PatchyBoy Esperto

    Messages:
    2,438
    Bangalore
    ^^ That must be because it is in MPH. @1000 RPM 24.48 MPH = 24.48*1.6 = 39.168 kmph

    Rajan
    2 people like this.
  8. nkrishnap

    nkrishnap Staff Member Janitor

    Messages:
    1,900
    Bangalore
    Bangalore
    Linea 1.3
    oops my bad. Thanks Rajan for point it out :)

    Now anybody has the drive and driven gears teeth numbers.
  9. My bad, I had selected 195/65 as tire size changed it to 195/60.
    geare_correted.JPG

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