Where to overdrive? Axle or T-case

[rcdriftmasterj]

Hi all, like the title states is there a benefit of doing overdrive at the axle or the t-case or does it not matter. Thanks for any advice!

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[CODYBOY]

Originally Posted by rcdriftmasterj

Hi all, like the title states is there a benefit of doing overdrive at the axle or the t-case or does it not matter. Thanks for any advice!

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I'm trying to think of how there would make a difference of reduction in the tranny, T-case or ring and pinion, and I don't think it matters.
Ernie

[hillbillyrc]

I could be wrong.

being able to run a stronger diff gear and overdrive at the t-case might be beneficial.

When I was looking in to axle gears for my e10 axles that I stuffed the axles full of scx10 axle parts. I kept reading that the overdrive gears weren't as strong as the standard gears and most said to was better to underdrive the rear axle. So I underdrove the rear and put standard gears in the front both in the heavy duty versions. Then I found a t-case that could be modded to run overdrive to the front axle.

[mass-hole]

Originally Posted by hillbillyrc

I could be wrong.



being able to run a stronger diff gear and overdrive at the t-case might be beneficial.



When I was looking in to axle gears for my e10 axles that I stuffed the axles full of scx10 axle parts. I kept reading that the overdrive gears weren't as strong as the standard gears and most said to was better to underdrive the rear axle. So I underdrove the rear and put standard gears in the front both in the heavy duty versions. Then I found a t-case that could be modded to run overdrive to the front axle.

This. The more gear reduction you have at the axle, the less stress the components in front of it should see.

By overdriving the axle you are reducing the gear reduction and thus everything before that axle could see more stress when you have to put a certain amount of torque to the ground.

Imagine you need 10 ft-lbs of wheel torque to overcome an obstacle. If you had a 5:1 diff ratio then that means you driveshafts, t-case etc. only have to contend with 2 ft-lbs of torque. If you then overdrove the front axle 20% to a 4:1 ratio, you front driveshaft is now contending with 2.5 ft-lbs to generate 10 ft-lbs at the wheel.

I just made these numbers up for simplicity’s sake.

[Voodoobrew]

Originally Posted by mass-hole

This. The more gear reduction you have at the axle, the less stress the components in front of it should see.

By overdriving the axle you are reducing the gear reduction and thus everything before that axle could see more stress when you have to put a certain amount of torque to the ground.

Imagine you need 10 ft-lbs of wheel torque to overcome an obstacle. If you had a 5:1 diff ratio then that means you driveshafts, t-case etc. only have to contend with 2 ft-lbs of torque. If you then overdrove the front axle 20% to a 4:1 ratio, you front driveshaft is now contending with 2.5 ft-lbs to generate 10 ft-lbs at the wheel.

I just made these numbers up for simplicity’s sake.

While I completely agree with this...
It depends on the axle and gears used. The scx10 doesn't have an under drive option as far as I know, neither does it have an optional transmission fix to under drive the rear.

A forward motor mounting solution paired with an overdriven transfer case in my opinion is better here. And if you change out the axles the upgrade remains.

Plus we are kind of limited to lower overdrive amounts in axles if we want the front and rear to match visualy.

You can go with trx4 axles which have a good deal of reduction then a transfer case/transmission that has 30% or more overdrive.

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[JohnRobHolmes]

A faster spinning driveshaft is better for torque twist and load on driveshafts, so keeping axle ratios as high as possible is always good.


-If underdrive gears are available, starting with this in the rear is generally a good bet. I haven't seen any "bad" underdrive gearsets around. I've seen overdrive gearsets have problems, but this isn't so much a problem with "overdrive gears" VS "underdrive gears" as much as what the axle was intended to accommodate and how the aftermarket gearset is designed to fit. Underdrive gears could potentially have too small of teeth or too little gearmesh and have a weak pinion, but so far that hasn't shown to be a problem.

-If this wasn't enough difference in ratio, next I would lean on a transfer case to accomplish this.

-If the transfer case has enough ratio difference, I would put underdrive in both front and rear axles and use the transfer case for all of the dig ratio. This gives the fastest driveshaft speed from T case to axles, which reduces torque twist and torque load on all parts between motor and axle.