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Old 03-08-2016, 08:00 PM   #1 (permalink)
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Gearbox change

G'day there,
I was thinking about a gearbox change , a diesel gearbox with a petrol engine gearbox.....as a diesel gearbox is much lower geared than a petrol engine gearbox you will get much better fuel economy,,,, just a thought,
Any input from you guys ?
Greetings,
Eddie

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Old 03-08-2016, 08:51 PM   #2 (permalink)
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I think it depends a lot on the speeds you drive. Could we have more details?
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Old 03-08-2016, 09:51 PM   #3 (permalink)
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G'day there
as i have details of the gear ratios for MY car it does not make much difference but it makes a difference, as i am a diesel lover and my past 4 cars were diesels ( but i have a petrol/gas car now) it makes a difference at the rev counter at any speed, for MY car the ratios are....final drive petrol 4.158... diesel 3.737
1st 13.753 13.222
2nd 7.954 7.149
3rd 5.231 5.025
4rd 3.920 3.838
5th 3.173 3.114
Reverse 13.433 12.545
In my diesel cars the rev counter at 90kmh (60mph)was about 1950 rpm but in my petrol/gas car it is about 2400rpm so it makes a difference , and that is what i was hinting at.
Hope i get some interesting feed back.
Greetings,
Eddie.
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Old 03-08-2016, 10:03 PM   #4 (permalink)
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Hi again
I had it all nicely set out petrol under petrol and diesel under diesel but it did not work out on the page, sorry about that i hope you can understand what i am on about.
Eddie
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Old 03-09-2016, 09:55 AM   #5 (permalink)
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At highway cruising at 60mph as you describe, the 1950rpms will save fuel, if your vehicle is like mine. My car showed about 2400rpms in stock form. I can put it in 4th gear now to get the same crusing ratio as I had in fifth before the swap. The benefit is about 4mpg.

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Old 03-09-2016, 04:30 PM   #6 (permalink)
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G'day there
James may i ask have you done a gearbox change with a diesel one ?
wel i think 4mpg is not bad at all with fuel prices here now about $1.68 per litre it has come down fron $2.38 per liter i think its going in the right direction, there is about 3.8 litre in a is gallon so we are taking for us it was about $9 dollars per gallon now at about $5.50 so its getting better.
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Old 03-09-2016, 05:07 PM   #7 (permalink)
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I expect this will be a very difficult swap in any vehicle that didn't already offer a diesel option. There are petrol cars that come from the factory with reasonable gearing already, though. For instance, my Insight is at 2175rpm @ 100km/h with a 3 cylinder engine, and my Civic is at 1960rpm @ 100km/h with a 4 cylinder engine.



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Old 03-10-2016, 10:26 PM   #8 (permalink)
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Quote:
Originally Posted by steddie View Post
I was thinking about a gearbox change , a diesel gearbox with a petrol engine gearbox.....as a diesel gearbox is much lower geared than a petrol engine gearbox you will get much better fuel economy,,,, just a thought,
Diesel seems to actually be higher geared, but anyway, it only works because of its higher torque at lower engine speeds, so fitting a Diesel gearbox into a gasser would eventually make it feel a bit "underpowered" since the torque multiplication would decrease.
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Old 03-11-2016, 12:22 AM   #9 (permalink)
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G'day there,
Thanx for that 'james', 'Ecky' and 'cripple rooster' it was only a thought of me to make the rev's lower so to save fuel, now that i have had so many great replies i have shelved that idea.
Greetings,
Eddie.
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Old 03-11-2016, 03:04 AM   #10 (permalink)
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What kind and year of car are we talking about? Some cars have had "econo" versions that might offer you a wide ratio tranny.

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