Trx4 rear end

[biev]

Throwing the idea around of running a trx4 portal rear end under my enduro. Should have overdrive gears in it as well. How much difference in overdrive will I have with od gears in the portal axle and flipping the stealth trans underdrive to front axle to compensate for rear end reduction. Hoping it's not too insane of an amount.

[mash914]

Interesting timing on your question - I was just doing some gear ratio comparisons between my enduro and my trx4.


The stock axle ratios:
Enduro - 30:8 -> 3.75:1
TRX-4 - 34:11 and 23:9(for the portal) so 3.1 x 2.56 -> 7.9:1


The stock enduro diff output is 52:20 ->2.6:1
If you put the max "underdrive" in, you keep the 2.6:1 towards the front but the back changes to 54:26 and 28:20, so overall 2.9:1


If you flip the gearbox you'd now have the 2.9:1 to the front and the 2.6:1 towards the back axle.


Combined with the stock axle, the overall ratio to the front will be 2.9 x 3.75 -> 10.9:1


To the rear will be 2.6 x 7.9 -> 20.5:1


From Traxxas, the biggest overdrive they have is a 35:10 which if you run through the math will change the 7.9 to 8.9.

The new ratio to the rear would be 2.6 x 8.9 -> 23.1:1....so worse unfortunately.


Using the stock 87:18 spur and pinion, your front / rear ratios would be:
52.5:1 / 99:1(or 112:1 with the overdrive!) - that's a lot of overdrive

I'm pretty sure this is right, but would appreciate if someone with more experience with this stuff would chime in and make sure my logic and numbers are correct.

[MAGNUMB]

Did you guys give this a go? If so, anything to report on? Was installing overdrive in the rear portal to compensate

[1beatjeep]

Originally Posted by mash914

Interesting timing on your question - I was just doing some gear ratio comparisons between my enduro and my trx4.


The stock axle ratios:
Enduro - 30:8 -> 3.75:1
TRX-4 - 34:11 and 23:9(for the portal) so 3.1 x 2.56 -> 7.9:1


The stock enduro diff output is 52:20 ->2.6:1
If you put the max "underdrive" in, you keep the 2.6:1 towards the front but the back changes to 54:26 and 28:20, so overall 2.9:1


If you flip the gearbox you'd now have the 2.9:1 to the front and the 2.6:1 towards the back axle.


Combined with the stock axle, the overall ratio to the front will be 2.9 x 3.75 -> 10.9:1


To the rear will be 2.6 x 7.9 -> 20.5:1


From Traxxas, the biggest overdrive they have is a 35:10 which if you run through the math will change the 7.9 to 8.9.

The new ratio to the rear would be 2.6 x 8.9 -> 23.1:1....so worse unfortunately.


Using the stock 87:18 spur and pinion, your front / rear ratios would be:
52.5:1 / 99:1(or 112:1 with the overdrive!) - that's a lot of overdrive

I'm pretty sure this is right, but would appreciate if someone with more experience with this stuff would chime in and make sure my logic and numbers are correct.

This is great info....