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Old 08-23-2022, 09:25 AM   #21 (permalink)
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The question seems to asking about mechanical efficiency of the transmission. perhaps confusing it with the overall economy

A lot of older transmissions would have the mainshaft run continuous from the clutch or torque converter to the output. Lower gears would use two sets of gears. Going to the secondary shaft and back to the primary shaft . Top gear is always 1:1, direct. The lower gears would have more losses as they would be transferring power to the secondary (lay) shaft and then back up to the main shaft

Most newer manual transmissions will have an input shaft and output shaft. So the transmission losses are similar across all the gears. Power is transferred across both shafts in all gears.

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Ecky (08-23-2022), Isaac Zachary (08-23-2022), serialk11r (08-23-2022)
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Old 08-23-2022, 03:36 PM   #22 (permalink)
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Varn you make a good point about the two sets of gears vs one. I was wondering what a ND Miata transmission looked like since Mazda bragged about the 1:1 6th gear being more efficient, and I noticed that there are a lot of transmissions out there that have 3 shafts, one pair which is inline and locked together for the 1:1 ratio. I had always thought transmissions came with just an input and output shaft.

I think in automotive applications however due to gear strength limitations there is a drop in efficiency from the gear ratios that deviate further from 1 as bigger gear pitch for strength = more sliding friction on the gears. I wouldn't be surprised if the typical 1st gear or some of the taller overdrives (like 0.6 ratio) were under 95% efficient.

Last edited by serialk11r; 08-23-2022 at 03:48 PM..
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