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Old 07-07-2017, 08:21 AM   #1
I wanna be Dave
 
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Default underdrive underdrive is it all that

I tryed the over drive underdrive set ups on my wraith ive tryed a few different set ups the best for me has been underdrives front and rear it worked great but i lost my rear gear set and i had the over drives laying around so i installed them up front and with nothing else changed i cant make any of the big climbs any more its like 2 tires wont get traction probably because the tires are spinning at differant speeds im woundering if this realy is the shiznik and i have my set up wrong or is this just a bad set up for a crawler the only time i herd of this in the 1:1 world is with subaru they used it to increse the handling on the dirt but they quickly did away with that set up my crawler rig is running bigger tires up front so basicly a overdrive underdrive set up and it works great so what am i missing what dose everyone else do for the over under mods and how is your rig set up
Thanks

I have new matching gears to install just woundering what everyone elses ideas are about this
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Old 07-11-2017, 01:07 PM   #2
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Default Re: underdrive underdrive is it all that

You probably liked the ud/ud set up more cause it kind of "tames" the rig. If you are running big tyres and od/od gears they add up to excessive wheel speed (and torque twist I guess) so you ought to be less trigger happy or resort to other means like a smaller motor gear or a bigger spur gear if you want to keep the od ones. I run deepwoods cr tyres and they are rather huge for 2.2 so I had to fix several things to make it work ok...

Last edited by Vagos2; 07-11-2017 at 01:10 PM.
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Old 07-11-2017, 01:14 PM   #3
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Default Re: underdrive underdrive is it all that

The advantage I see is running more teeth on the ring gear equates to less torque twist, meaning on a steep climb, you are less likely to start lifting that front tire. Of course you lose top end, but you gain control and torque. When I had my wraith, it definitely helped stop that torque twist and allowed me to climb steeper grades.
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Old 07-11-2017, 01:47 PM   #4
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Default Re: underdrive underdrive is it all that

On my wraith I like the underdrive gears front and rear my new ones are installed and ready for axial fest
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Old 07-12-2017, 04:25 AM   #5
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Default Re: underdrive underdrive is it all that

Quote:
Originally Posted by ferp420 View Post
On my wraith I like the underdrive gears front and rear my new ones are installed and ready for axial fest
Is it not just easier to fit a bigger spur or smaller pinion? I thought fitting UD in front and back was the same as gearing down at the spur / pinion
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Old 07-12-2017, 06:12 AM   #6
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Default Re: underdrive underdrive is it all that

Final drive ratio may be the same, but it also seems to have an effect on torque twist.

I just received my 11/38 gears for the rear, I wonder if it will help with turning and climbing compared to stock 13/38 I'm keeping in the font. Or is it too small of a difference to change handling.
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Old 07-27-2017, 12:24 AM   #7
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Default Re: underdrive underdrive is it all that

I have heard many of my senior crawler fans said that the UD front and rear are the best in gear mesh. For durability sake, I think I would try this setups next time on my Wraith
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Old 10-09-2017, 11:24 PM   #8
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Default Re: underdrive underdrive is it all that

I religiously ran over/under on my truck before I swapped to scx10.2 axles. It works awesome if set up right, more weight on front/softer foams definitely helps. Although running the same gear ratio feels more solid in a way, I could pull crazy lines with the overdrive
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Old 10-11-2017, 05:56 AM   #9
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Default Re: underdrive underdrive is it all that

I did a couple of runs with underdrive on the rear of my Wraith and it would have made me jump with joy if I wasn't overweight and tired all the time!

Better turning circle, front axle more likely to stay on the ground when things get steep so steering when climbing is now a real thing, and I can still swing the rear around on loose stuff with a blip of the throttle. It did reduce speed overall a bit, so I switched back to 12/56 (3s 27T) for general fooling around.
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Old 10-11-2017, 07:47 AM   #10
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Default Re: underdrive underdrive is it all that

OD/UD is great for making a tight turning radius and "should be" beneficial on hill climbs.
This can depend on your vehicle setup and certainly is impacted by foams and tire type/diameter.

On a climb the front should pull harder, which will start to put a hair of bind on the tires forcing them to grip.
If your tires aren't sticky (or hard foams) then you will lack the grip though.
If your tires are too big then the ratio might be too much.


So, if OD/UD is causing you to lose grip, you might be happier with a set of standard HD gears up front and UD in the rear.
That way you still get a little help with turning radius and climbing, but the ratio isn't so much to cause you to lose grip.

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Old 10-15-2017, 12:36 PM   #11
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Default Re: underdrive underdrive is it all that

I'm running underdrive in the rear of my Wraith. In conjunction with the Vanquish VVDs up front, turning radius is vastly improved! I also like how the front "pulls" over things now.
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