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Thread: 5th gear ratio mod

  1. #1
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    5th gear ratio mod

    Hi all, have been reading up on changing the 5th gear ratio to help with fuel economy on the highway.
    Back story is I will be buying a polo Tdi 1.9 to drive from Sydney to Goulburn for work, wanted to get 5th gear sitting as low as possible in the rev range as I’ll be sitting at about 120kph.
    As I don’t physically have a car yet I’m a little unsure what the gearbox code itself is, and if a 5th gear ratio change is available/possible

    Any advice would be great.

  2. #2
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    I looked into this a while back and the only option I found was to fit a 6 speed gearbox. I couldn't even find a taller final drive option

    Great choice for that commute, BTW
    Last edited by kaanage; 11-05-2022 at 07:29 PM.
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  3. #3
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    Quote Originally Posted by kaanage View Post
    I looked into this a while back and the only option I found was to fit a 6 speed gearbox. I couldn't even find a taller final drive option

    Great choice for that commute, BTW
    I would be a bit concerned about the pull from Picton Road up to Mittagong with a higher ratio and it would be a hard way to find out the installed ratio was too high.

  4. #4
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    Quote Originally Posted by kaanage View Post
    I looked into this a while back and the only option I found was to fit a 6 speed gearbox. I couldn't even find a taller final drive option

    Great choice for that commute, BTW
    Was that due to the type of gearbox the polo has? What is the gearbox code for them?

    I’ve found a couple different places overseas that supply kits to change the ratio but without knowing the trans code I can’t confirm of these are the correct ones

    Did you end up fitting a 6 speed ?

  5. #5
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    Quote Originally Posted by Ozsko View Post
    I would be a bit concerned about the pull from Picton Road up to Mittagong with a higher ratio and it would be a hard way to find out the installed ratio was too high.
    So far from what I’ve read, a .592 ratio 5th gear will see about 1900rpm at 120kph which is right about where I want it and we’ll within the torque curve. Obviously anything under 90th kms will be interesting but the hours which I drive there is generally little to no traffic

  6. #6
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    I just went by comments on the UK forums about the options (or rather lack thereof) for internal ratios for the PoD.

    I never ended up modding the drivetrain. The ring gear size issue stopped me getting the LSD and the 6 speed box is about 20kg heavier than the 5 speed so I didn't think there was enough benefit.

    Worrying about one climb on the route is silly - you can always shift down.

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  7. #7
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    Quote Originally Posted by kaanage View Post
    I just went by comments on the UK forums about the options (or rather lack thereof) for internal ratios for the PoD.

    I never ended up modding the drivetrain. The ring gear size issue stopped me getting the LSD and the 6 speed box is about 20kg heavier than the 5 speed so I didn't think there was enough benefit.

    Worrying about one climb on the route is silly - you can always shift down.

    Sent from my moto g31(w) using Tapatalk
    What 6 speed?

    There’s ~3kg difference between a 02A/J and a 02S/R


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  8. #8
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    I was thinking of the 02M as I don't think the 02S is strong enough for a tdi.

    Then again this guy put one into his souped up GTI so it may work
    UK Polo GTI 320BHP

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  9. #9
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    Quote Originally Posted by kaanage View Post
    I was thinking of the 02M as I don't think the 02S is strong enough for a tdi.

    Then again this guy put one into his souped up GTI so it may work
    UK Polo GTI 320BHP

    Sent from my moto g31(w) using Tapatalk
    02S comes in our GTD’s/MK5 diesels


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  10. #10
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    Quote Originally Posted by kaanage View Post
    I just went by comments on the UK forums about the options (or rather lack thereof) for internal ratios for the PoD.

    I never ended up modding the drivetrain. The ring gear size issue stopped me getting the LSD and the 6 speed box is about 20kg heavier than the 5 speed so I didn't think there was enough benefit.

    Worrying about one climb on the route is silly - you can always shift down.

    Sent from my moto g31(w) using Tapatalk
    Was that the lack of options due to what box the polo's have? Can i ask what the gearbox code is for a polo TDi or do they differ?

    So far darkside development seem to have all 5th gear pars available (Gearbox compatibility depending) and would be alot cheaper and easier than swapping to a 6 speed which is also an option if there is no 5th gear compatible.
    Darkside Developments - 5 Speed 02J, 02A ,02B, 02C & 02Z - .592, .622, .658, .681, .700, .717 & .744 5th Gear Sets

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