# Can anyone explain Gearbox Ratio's

Discussion in 'Tech/Mech General' started by fred flintstone, Aug 14, 2016.

1. ### fred flintstoneFunster

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I have a Peugeot Pilote with a 5 speed box.
I recently replaced the 5th gears.
The gears in my box were 33/56 which is 0.59/1.
The only replacements I could get were 35/58 which is 0.60/1 (approximately 3% lower geared).

My question is will I have more torque with the new gears or will it be a longer gear giving a higher top speed.

Maths was never my strongest subject

2. ### BoringfrogFunster

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If it's lower geared you will have a lower top speed and it will feel like you have more torque.

I think

3. ### John LaidlerFunster

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It is higher geared, but it may not mean you will go faster, just very slightly lower revs for the same speed. But the difference in your case is negligible I think, 0.59 versus 0.6 is nothing.

I'm assuming the smaller gear is the input one and it isn't an "overdrive", in which case the reverse* would hold.

*no pun intended!

Last edited: Aug 14, 2016

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pass.

5. ### DP_JAYFunsterLife Member

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Should those numbers not be the other way round?
56/33 = 1.69 - 1
58/35 = 1.65 - 1
Your new gears are lower/ shorter which will mean higher revs and the feeling of more power in fifth,though on!y very slightly.
I went from 1.7-1 to 1.54 -1 which made a difference of 800rpm @ 60mph.

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6. ### John LaidlerFunster

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Which was my point, which is the input gear? I know nothing about pug gearboxes but I understand mechanics.

7. ### BoringfrogFunster

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What do you mean input gear? I think the smaller gear drives the driveshafts.

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8. ### John LaidlerFunster

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If that is so, and I have no reason to doubt you, then the arrangement is the opposite of what I thought. By input I meant the gear which is being driven by the engine which in turn drives the gear connected through the final drive the wheels.

9. ### chaserFunster

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No nowt other than old cars always quoted gear ratios for some reason and top was always 1-1 then overdrive started coming in and it got as it was 1-25 or so as I say don't know owt about it other than that but it must have something to do with it.

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10. ### BaycottFunster

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I don't know why i'm reading this post, I don't understand a word of it

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11. ### BoringfrogFunster

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I thought I did, not sure now!

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12. ### BoringfrogFunster

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So the gear driven by the engine is the larger.

Help, my brain hurts.

13. ### BoringfrogFunster

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14. ### DP_JAYFunsterLife Member

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Yea, as per a bike gearset
Large gear at front driving smaller gears at rear
Each time you change to a smaller gear you change to a higher ratio so less turns of the pedals & more turns of the wheel

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15. ### DP_JAYFunsterLife Member

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Yes

16. ### funflairFunsterLife Member

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To answer at least part of the original question it doesn't alter the torque at all as that is a product of the engine characteristics not the gearbox.

On the gearing it looks me to be a slightly lower overdrive, so a few more revs for the same cruising speed.

Martin

17. ### John LaidlerFunster

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Oops, no, the whole point of the gearbox is to increase the torque at the wheels, the lower the gear the greater the torque. For example, an overall gear ration of 1:2 would double the torque from the engine. Conversely, the higher the gear the lower the torque.

But to answer @stooo 's question - I wouldn't worry too much. The new gears are indeed a slightly lower ratio but the difference is only 2%, so I doubt you will even notice it.

18. ### funflairFunsterLife Member

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But the engine produces torque via the combustion process which in turn produces power which is the torque X engine speed, the gearbox's job is to match the engines most efficient operating rev range to the desired road speed. Or that's the way I see it anyway.

Martin

19. ### JJFunster

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The ratio of the gear to talc/washing power/Vim that you get for your money is totally dependent on the decency of your supplier/dealer...

If you talk too much about him, he might be upset.

I hope this helps.

JJ

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