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-   -   TRX4 final axle gear ratio? (http://www.rccrawler.com/forum/traxxas-crawlers/596986-trx4-final-axle-gear-ratio.html)

Stan3535 03-25-2018 08:54 PM

TRX4 final axle gear ratio?
 
I get confused due to the portal gears when trying to figure out the axle gear ratio. I am thinking of putting the Traxxas front Portal axle on the rear of a Axial Yeti so I can have 4WS, Portal axle, 2 speed, and diff lock. Can anyone help me out when it comes to figuring out the final gear ratio to see if is compatible with any of the Axial diff ratios? Axial diff gear ratio's are 38/13 (2.9), 36/14 (2.5), and 43/13 (3.3). Thanks a bunch! "thumbsup"

CODYBOY 03-25-2018 09:06 PM

Re: TRX4 final axle gear ratio?
 
Quote:

Originally Posted by Stan3535 (Post 5814698)
I get confused due to the portal gears when trying to figure out the axle gear ratio. I am thinking of putting the Traxxas front Portal axle on the rear of a Axial Yeti so I can have 4WS, Portal axle, 2 speed, and diff lock. Can anyone help me out when it comes to figuring out the final gear ratio to see if is compatible with any of the Axial diff ratios? Axial diff gear ratio's are 38/13 (2.9), 36/14 (2.5), and 43/13 (3.3). Thanks a bunch! "thumbsup"

Just a little info for you. The portal gear ratio is 2.3:1 so that would reduce the stock ratio by more than 1/2. So your front axle would be dragging the rear portal all over. About the only way you could make it work would be to use a transfer case with gearing that add that 2.3:1 back to the rear drive ratio. I don't think what you want to do would work very well. JMO "thumbsup"
Ernie

Here is a chart of numbers I crunched when building my ascender portal axles. The final numbers may not work for you but the formula would.

http://i1264.photobucket.com/albums/...0e549d7bf5.jpg

Stan3535 03-26-2018 09:56 AM

Re: TRX4 final axle gear ratio?
 
Thanks Ernie. I saved that chart "thumbsup"

OldNASCARCrawler 03-28-2018 09:23 AM

Re: TRX4 final axle gear ratio?
 
Great Work

Thanks

Voodoobrew 08-11-2018 12:01 AM

Re: TRX4 final axle gear ratio?
 
I think your numbers are off, Diff gears are 34/11 or 3.09/1

Gear Options:

Underdrive: TRA8288
Standard: TRA8279R <--------this one
Overdrive: TRA8287

(edit) maybe those aren't the dif gears, TRA8282 are dif gears but look different they are 18/11 or 1.38/1

and the portal gears look like 23/10 or 2.3/1 TRA8258 and TRA8257
I cant count the teeth in the picture might be 23/9 which would make the whole axle 7.9/1

I'm just looking at the parts at a online hobby store and counting teeth. not owning a trx4 to see which gears go where.

I think the total axle reduction (front, don't know if rear is different) is 2.3*3.09=7.11
(numbers are rounded)

my calculations for the transmission are also
1st gear 36/18 or 2:1
2nd gear 24/30 or 0.8:1

to calculate your final gear rato
main * trans * diff * portal
1st gear = (spur/pinion)*(36/18)*(34/11)*(23/9)
ex stock = (45/11) * 2 * 3.09 * 2.56 = 64.72
easiest1 = (45/11)*15.8=64.63 first gear
2nd gear= (spur/pinion)*(24/30)*(34/11)*(23/9)
easiest2 = (45/11)*6.32=25.85 second gear

So if you wanted you could probably get a 9T 48P pinon and 68T 48P spur and have 119.36/1 first gear and 47.75/1 second gear reduction.
I don't know if this spur is available, if it is it probably dosen't say trx4 on the package. But it looks like a fairly basic spur to me.

Voodoobrew 08-26-2018 06:02 PM

Re: TRX4 final axle gear ratio?
 
I miss read this, but how did you intend to mount the Traxxas portal axles to a axial Diff? oh, you mean match it to the front diff...
nevermind, Im slow

4kids crawlin 09-30-2018 09:35 PM

Re: TRX4 final axle gear ratio?
 
I know this is an older post but how hard would it be to put a set of trx portal axles on a scx10 ii? And would the gearing be so low that it would be useless? Thanks for any help.

Sent from my SM-G930V using Tapatalk

Jeepy84 11-18-2018 07:23 PM

Re: TRX4 final axle gear ratio?
 
Quote:

Originally Posted by 4kids crawlin (Post 5872590)
I know this is an older post but how hard would it be to put a set of trx portal axles on a scx10 ii? And would the gearing be so low that it would be useless? Thanks for any help.

Sent from my SM-G930V using Tapatalk

I did this but have a gcm scale transmission so my initial transmission output ratio is slightly different thanthe 10.2 kit trans. Top speed on a 1900kv brushless 3s is about walking pace though. Putting the axles underneath required custom length links pretty much all around.

I was thinking of putting a trx axle on the front of a toyzuki v2 with an OD gear set, leaving the AR44 I have on it in the rear. Haven't run the numbers but I'm hopeful the OD gears and transfer case OD will overcome the difference between front to rear. Maybe even still have a little OD upfront, this thread should help a lot.
https://uploads.tapatalk-cdn.com/201...e68a5f08fc.jpg

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Jeepy84 11-18-2018 07:52 PM

Re: TRX4 final axle gear ratio?
 
After crunching numbers, nope. Gonna have to lose the rear leaf AR44s and put the other trx axle back there on links. Final ratio difference front to rear is 1.67. Unless I run a secondary reduction to the rear axle, which is probably doable, but hard to justify, given the space I would have to work it into.

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