General automotive: Why is the differential geared down?
04-12-2012, 10:04 PM
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General automotive: Why is the differential geared down? Hi,
This is probably a stupid question, so excuse my dumbness, but why is the their a final drive ratio? Couldn't the differential be 1:1 and have all the gearing down happen in the transmission?
This is probably a stupid question, so excuse my dumbness, but why is the their a final drive ratio? Couldn't the differential be 1:1 and have all the gearing down happen in the transmission?
04-13-2012, 03:54 PM
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Because then you'd need 3-4X the torque capacity in
the driveshaft and U-joints, for same rear wheel torque.
That's extra rotating mass for the required stiffness.
And you'd need a bigger pinion gear, because the ring
teeth are not that far from their limits. That'd be a heavier
pumpkin all told.
But transaxles basically do this (driveshaft spins at motor
RPM, all reduction in the unified trans / diff casing).
the driveshaft and U-joints, for same rear wheel torque.
That's extra rotating mass for the required stiffness.
And you'd need a bigger pinion gear, because the ring
teeth are not that far from their limits. That'd be a heavier
pumpkin all told.
But transaxles basically do this (driveshaft spins at motor
RPM, all reduction in the unified trans / diff casing).
04-14-2012, 12:22 AM
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Torque multiplication in stages. Just like jimmy said. The more gear sets you can multiply or reduce torque, the better.
That's why on big time heavy trucks like the mining trucks that are The size of a house, they have planetaries in the wheel hub itself to spread the gear reduction forces out more.
That's why on big time heavy trucks like the mining trucks that are The size of a house, they have planetaries in the wheel hub itself to spread the gear reduction forces out more.
04-17-2012, 11:50 AM
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I don't see how making the final drive 1:1 and all the gears in the trans modified to make the gears still similar to what it would be would require heavier DS and ujoints? You'd still be applying the same force to the driveshaft. I think that you would, however, need a beefier transmission, but a heavier duty rear end may not be required.
Imagine what a 1:1 gear ratio ring & pinion would look like
Imagine what a 1:1 gear ratio ring & pinion would look like
04-17-2012, 12:03 PM
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I don't see how making the final drive 1:1 and all the gears in the trans modified to make the gears still similar to what it would be would require heavier DS and ujoints? You'd still be applying the same force to the driveshaft. I think that you would, however, need a beefier transmission, but a heavier duty rear end may not be required.
Imagine what a 1:1 gear ratio ring & pinion would look like
Imagine what a 1:1 gear ratio ring & pinion would look like
04-17-2012, 12:32 PM
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Now that I did some thinking about it, I get it. It's like loading furniture. 2 people, 1 pushing 1 pulling is better than 1 strong person pushing. I retract my statement.
