2-speed transmission upgrade using Axial Yeti parts

[fyrstormer]

Around the beginning of 2017 I bought the SSD 2-speed transmission kit, but I was never happy with its performance. There was too much slop in the shifter clutch, the output shaft wobbled and flexed the entire gearbox housing, and the teeth on one of the high-speed gears weren't blunted properly so they bottomed-out in the spaces between the teeth on the other gear, causing an awful whizzing sound whenever the truck was running in high gear.

https://www.youtube.com/watch?v=ucnsOcX2nqg

I went through three SSD 2-speed kits and they all had these same problems, so eventually I gave up and the truck just sat on the shelf while I waited for the official Axial 2-speed kit.

Well, that 2-speed kit never materialized. Axial just left us hanging. That sucked. However, they did release a shift-fork that would fit the SCX10 II's gearbox housing, and the Yeti 2-speed gears are a direct fit. So eventually I got around to buying the Yeti 2-speed kit and I installed it a couple days ago.



I did end up having to use one part from the SSD 2-speed kit -- the shift-fork linkage rod. The one that comes with the Axial Yeti 2-speed kit is designed to thread into the shift-fork, but the SCX10 II compatible shift-fork just has a bare unthreaded hole. I had to grind-down one side of the shift-fork to get the SSD linkage rod to fit far enough that the E-clip could snap into its groove, but that doesn't affect the fork's ability to move far enough to shift solidly into both gears. (I checked the positions of the shifter parts before grinding to make sure I should grind all the excess material off one side, instead of grinding half-and-half off both sides.)



I was also unhappy with the narrow gear range offered by the SSD 2-speed kit, though that wasn't their fault -- the gearbox is sized to fit a 26t 48p input gear, and there isn't even a smidge of extra space for a larger gear to fit. Well, the Axial Yeti 2-speed kit came with an optional 26t 48p output gear, intended to mesh with a 28t 48p input gear, and I damn well wanted to use it because I wanted a wider gear range. With the intended setup, the truck's top speed was 5mph in low gear and 9mph in high gear, which was pretty pointless. I used the awesome power of elementary-school arithmetic to determine I could get an 11mph top speed in high gear if I could run the 28/26 optional gears instead, without having to compromise on torque in low gear by gearing-up the motor pinion. So I got out my Dremel (which I use so often I might as well just leave it out all the time), and I started grinding away plastic from the inside of the gearbox housing until the 28t input gear fit. As you can see above, it worked -- I didn't breach the side of the housing despite not having much plastic to work with in the first place.



I took this picture just before I buttoned-up the gearbox housing. You can see the 28/26 2nd-speed gears sticking out the back; the 28t gear is actually made by Hot Racing, intended as an upgrade for the sintered-metal gears used in the RTR Yeti, but it works just as well here. This way I have a complete set of hardened-steel gears in my SCX10 II's gearbox.

This setup works much better. It's quieter and the Axial output shaft spins true like it should, and as I calculated I get top speeds of 5mph and 11mph, which is on-par with my Vaterra Ascender. If there's anyone else who's looking for a better 2-speed setup and doesn't want to have to go with the older, higher center-of-gravity RC4WD AX2 transmission for the Wraith, this is a good solution.

[MattySlimz1987]

Thankyou for sharing this with us. I remember watching your video back in February before I bought my 10ii because I was dumbfounded by the fact that this company (Axial) has a kit truck with a 2-speed capable trans, yet they didn't make the parts to do the conv. Consumers had to rely on a good aftermarket manufacturer to save the day, this stays true even still to this day! It's great that you did some trial and error testing to find what you wanted and that you shared it, looks to be an awesome improvement.

[Peaker]

Pretty bummed to read this after i ordered the SSD 2 speed kit.

Then again the Axial 2 speed kit for the yeti i might be able to find within the EU.

And now i am pretty sure the SSD kit will get taken by customs and have its price doubled

[Peaker]

Aside for my car setting fire to the used 35T motor i put in it for the maiden voyage i had no problems, no flexing gearbox and only a little different sound in between the 2 gears and FF / REW motion as it it pretty normal,,,, well it was that way with my TF2 too.
I would not call my truck loud compared to what i remember the TF2 being and my friends TRX 4

Only need to replace shocks as i was not lucky getting them to hold oil, was going to do this anyway but did not expect to do it so fast.


PS. just the SSD 2-speed kit i have thrown in the gearbox.

PPS. i think i will play it down to a 45T motor when the current one need replacement, the truck sure isent too slow with the 35T.
We have some transit time in between driving spots where we drive, and no need to exit first gear as its plenty fast to keep up with us ( one heart attach survivor and me sounding like a steam train with 25% lung capacity left )

[fyrstormer]

When you installed the 2-speed transmission, did you notice one of the gears felt very sharp on the edges of the teeth? If you didn't notice this, perhaps SSD fixed the problem.

I have trouble with the shocks leaking also. I'm going to use some Traxxas "X-rings" to seal the shocks better.

[Peaker]

No. I was aware of this potential issue, so i looked over all gears in the gear box, and i found them to be just fine both the axial ones and the ones coming with the kit.

They are off course much smaller than the gears i have been used to making and handling in my last job, but all in all they seem to be fine.

I was on my #2 drive with the car yesterday and the car are a bit more noisy than my friends TRX 4 but no way near what i have been used to driving the TF2 the past years.

It is funny with those gear boxes, my friend just build a tow truck on the Cross PG4L, and he say there is another guy that have the same 2 speed gearbox in another Cross truck and his gearbox are just insane loud where i would rank the one in my friends as about as loud as my SCX 10 II.
Truck Cross PG4L Tow Truck - 2017 - Måtte sgu lige have en Cross ...

My friend have a 6 x 6 build with a 3 speed gearbox from Tamiya, and that is and always have been a loud gearbox, both when in his Tamiya trucks and in the build ( he have 3 of those gearboxes and we tried a lot on them to make them more quiet )

I wish the gear kit came with 2 new gearing's, the ones now just both seem too fast for a scaler, i have only tried #2 gear to see the speed, i dont feel like a need to use that in a off-road situation, other maybe than a photo ops where you really would like to see some mud / water flying in the picture.
I would prefer a gearing where #1 are slower then current #1 and #2 are same or maybe a little bit faster than current #1 gear.

PS. using 3 cell as always.

PPS. my dampers was leaking at the top, so i will just seal that threading with a little plumbers thread tape next time i have them apart, and i have a set of G made RSD coming to replace them

[fyrstormer]

That's odd. My TRX-4 is definitely louder than my SCX10 II, now that I've replaced the gears in the SCX10 II. The TRX-4 has so many gears, though, and that's why it's noisy.

My shocks also leaked at the top, but that stopped after I got Team STRC shock bodies. They still leak at the bottom though, so hopefully the Traxxas X-rings will fix that problem.

[Peaker]

I wish people making after market gearboxes would go 1 step further and make them sealed so you could have a little oil in there.

[fyrstormer]

You don't need liquid oil. Grease works just fine. The gears in RC transmissions aren't subjected to anywhere near the same loads that real car transmissions are. The gears only need a microscopic coating of grease to keep them properly lubricated, so even if most of the grease gets flung off, it won't affect the gears' operation.

[Taper]

Great job!

[fyrstormer]

Originally Posted by Taper

Great job!

Thanks! I still have this transmission and it still works fine. Nice and quiet too, unlike the SSD transmission I tried first. That may seem like a weird thing to care about (I know my demo video on Youtube got a bunch of hate from dudebros who think everything in the world should be made of rusty steel and belching diesel smoke), but when you're trying to go for a nice quiet walk in the woods and the loudest thing you can hear isn't the wind through the trees but the incessant whine of badly-meshing gears, then you understand why a quiet transmission matters.