# Maybe a stupid question... Ring gear sizes...

I was just sitting in a very boring training class here at work, and my mind started wondering. I was thinking about the 292ci motor and how
its longer stroke helps increase the torque at lower RPMs.
I was just wondering if this would apply to differentials as well.
Think of it this way... if you had two different theoretical axles, equal in every single way except for the diameter of the ring gear, would there be more or less leverage (torque) applied to the axle shafts with a larger ring gear vs. a smaller one? (10.5" and a 8.5" gear respectively, but with the same ratio)
I was just thinking that the outer edge of the larger gear would have to be traveling faster than the smaller gear in order to make a complete revolution in the same period of time...but would there be any loss or gain because of the different diameter ring gears?
Again, this is assuming all other things being equal, where weight and ground clearance and tire size are of no relavance, and the tests were conducted on a rear-wheel Dyno setup.
Forgive me if this is completely asinine. I'm just *really* bored today ;-)
~jp
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Your logic has merit but the problem with it is that a bigger ring gear also has a bigger pinion diameter at tooth contact area with same final drive ratio so the force applied to gear faces may be less but the same net result is found on axle shafts vs a smaller ring and pinion of same ratio and same input torque. In theory the bigger gear would be more efficent at same high axle torque load because the contact area would have lower shearing forces on it because of reduced pressure but then there is also a bit more surface area to shear too. ----------------- TheSnoMan.com
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Interesting... I kinda started thinking along those same lines after posting, but you put it into words where I could not.
I figured that in a real world application, any gains would be negated by the larger mass of the gears and entire rotating assembly--hence my "all other things being equal" disclaimer.
Still, good to hear it from someone else. I learn more from the discussions that go into theory than I do from the posts that just say "do this and the problem will go away"... :-)
~jp
SnoMan wrote:

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