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Thread: Changing gear ratio on manual transmission

  1. #1
    Senior Member Chef Groleau's Avatar
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    Changing gear ratio on manual transmission

    Just wondering if anyone has or looked into regearing the transmission.

    Ive driven 7500km on my new micra. I love the car, great in the city. But mileage on the highway sucks. 3000 rpm at 100km/h, thats rather high. I tend to be doing 120-140+ a fair bit. So its becoming a thirsty car.

    I find first gear a wee bit low I usually end up shifting by 20km/h and often end up skipping 3rd or 4th depending of my driving. And usually in 5th by the time I am doing 80 on highway....even 50 in town. Ive never really had to downshift to pass anyone.

    I am seriously considering ripping my transmission out. Put a slightly taller first gear. 5th gear (or something close to the current gear) would then become 4th, id get a taller 5th gear highway cruising. 2nd and 3rd id adjust to fit nicely with the new ratio of the other gear.

    Im not worried about voiding the warranty, ill provably end up voiding it pretty soon anyways. Im not one to pay over priced mechanics to do my maintenance.

    Any thought?


    Last edited by Chef Groleau; 04-17-2017 at 05:17 AM.

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    Senior Member geodude's Avatar
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    Many of us on here would love a more highway cruise-friendly fifth gear. I'm however not one to do such a big job to change it, but I'd love to see the fruits of someone else's labour.
    First car: 1984 silver Nissan Micra
    Current car: 2016 Gun Metallic Nissan Micra SV

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    Senior Member Chef Groleau's Avatar
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    Ive rebuilt two engines in the past. Never took a transmission apart before tho. Guess theres a first for everything, Im gona do a bit of research on this.

    Do you know if the nissan versa has the same trasmission than the micra?

    On a side note, I just ordered a short ram intake 5 min ago

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    Senior Member AlphaMicra's Avatar
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    Taller tires help quite a bit.

    In our culture obsessed with absurd excess, the Nissan Micra is my counterculture car of choice.
    Be sure to visit my blog at mymicra.com!

        __________________________________________

        click to view fuel log View my fuel log 2015 Micra SV manual: 6.4 L/100 km ... 44.3 mpg (Imp) ... 15.7 km/L ... 36.9 mpg (US) ...


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    Senior Member geodude's Avatar
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    Quote Originally Posted by Chef Groleau View Post
    Ive rebuilt two engines in the past. Never took a transmission apart before tho. Guess theres a first for everything, Im gona do a bit of research on this.

    Do you know if the nissan versa has the same trasmission than the micra?

    On a side note, I just ordered a short ram intake 5 min ago
    Have fun with the intake! Loving mine.
    First car: 1984 silver Nissan Micra
    Current car: 2016 Gun Metallic Nissan Micra SV

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    i do what alpha micra does, only i gear lower for acceleration...205/40/16..do the math..lol

    fiddle with tire diameters...still cheaper than trans and sooooo easy to change!
    2015 Micra S (manual)
    no A/C /no power options
    Feb 2015 build

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    Senior Member Chef Groleau's Avatar
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    Quote Originally Posted by AlphaMicra View Post
    Taller tires help quite a bit.

    I know you do not mean this much taller tires.... But when ever I hear that all I can think of is a Donk car.
    Lol
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    Administrator MetroMPG's Avatar
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    swapping 5th gear or final drive

    Changing individual gear ratios within the transmission is a very big job. (Eg. 1st gear).

    It's better to look at what other cars used the same transmission with different ratios, or the same spacing on the input & output shafts (with different 5th gear ratios).

    Changing just 5th gear...

    This can be relatively easy... if the gears are OUTSIDE the transmisson case under a stamped steel cover (like most FWD cars I've owned).

    I know of Saturn owners who have done a 5th gear swap for lower highway RPM & better fuel economy:

    ---> Saturn S-Series 5th Gear Swap (images in this thread are broken, but the text is still informative).

    The trick is finding a car with compatible gearing as a source of the parts. (Saturn had several different engines & transmissions that were all interchangeable).

    Unfortunately, the last time I checked (2015), the Versa sedan & Versa Note (same HR16DE engine as Micra) transmission was identical to the Micra's, so there's nothing helpful there.

    If no alternative 5th gearsets are out there (I'd be surprised if that's the case), you could have a set machined. I know of a couple of people who went that route, but it's very expensive. (Over $1k).

    Changing the final drive...

    I did this in my Firefly, by swapping the entire transaxle (same gearing 1-5, just taller final drive) from a 4-cylinder Suzuki Swift. When you change the final drive, you change performance in ALL gears, relative to stock. Note: this will hurt acceleration, if that's a concern of yours.

    ---> Project 'nerd gear': taller tranny transplant nets +5.2% MPG

    I think the easiest route for someone interested in doing this would be researching 5th gear ratios and measuring the diameters & distance between the input & output shafts on other Nissan 4-cylinder FWD cars. EG. Sentra, Stanza, Altima were more powerful, so 5th gear ratio is probably taller (numerically lower). If you find something that's identical to the measurements on the Micra trans, then swapping just the 5th gearset may be doable.

    Juke uses a 1.6 turbo, so the transmission bellhousing is probably the same as the Micra's. Not sure about the internal measurements though.

    As Alpha points out, you can swap larger diameter tires, but the difference won't be as big as a gearing change. Also, larger diameter tires raises the ride height, which also increases aerodynamic drag (thus bringing fuel economy back down). You could use lowering springs to get it back to normal, or lower.

    I do hope someone investigates this, so when I eventually get a Micra, all the answers will be here.

        __________________________________________

        click to view fuel log View my fuel log 2015 Micra S manual: 5.0 L/100 km ... 56.5 mpg (Imp) ... 20.0 km/L ... 47.0 mpg (US) ...


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    Senior Member Chef Groleau's Avatar
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    Well, stopped at the dealership. Found out that the 2017 versa and 2017 micra manual transmission is pretty much the same. Different model code number, but the only difference i found was the micra gets a speedometer drive gear and the versa does not.

    At least I now know I can use a Chilton maintenance manual for a Nissan Versa to walk me thru the steps of disassembling the transmission.
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  11. #10
    Administrator MetroMPG's Avatar
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    Now it's just a matter of finding different gears that will fit the shaft spacing.


        __________________________________________

        click to view fuel log View my fuel log 2015 Micra S manual: 5.0 L/100 km ... 56.5 mpg (Imp) ... 20.0 km/L ... 47.0 mpg (US) ...


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