Transmission Clicking Fix

[Forker45]

If you have a TRX-4 Sport with a clicking / ticking transmission and haven’t been able to eliminate it with the normal suggestions then this may be helpful. I put a video together showing what causes the issue and how I solved it. I can’t say if this will work for 2-speed trans but the same premise could be applied.



My TRX-4 Sport Kit had a clicking sound under a load from day one. I found possible solutions searching the forum and tried them all. I checked driveshaft phasing, transmission front/rear output phasing, replace driveshafts w/ MIP units, & inspected trans gears for debris. None of these eliminated the clicking sound. But when I inspected the trans gears I noticed an issue that led me toward a final solution.

I found the transfer gear on the main shaft had been rubbing the bearing boss of the transmission case. You can see the debris in the bearing pocket in the photo below. For reference the truck is less than a month old and doesn’t have tons of hours running, so I know it’s not debris from wear or running.





The cause of the issue was due to excessive endplay of the main output shaft. Without going too deep into the details, I found the solution to be shimming the spacer side of the output shaft and also between the inner bearing race and transfer gear pin. If you’re interested in the details, watch my YouTube video as I explain it there.



On the output shaft side I used a 5.4x9.5x0.2mm Arrma shim (ARA709057) because it’s what I had on hand. Note: the OD of the Arrma shim is too big to use under the gear pin on the transfer gear side.





To shim under the transfer gear pin, I used 4X 5x8x0.25mm clutch shims I happened to have around from my old HPI Savage X 4.6.





The combination of shimming on both sides reduced the endplay to where the transfer gear no longer contacts the case but still spins freely.

You could use 2x Traxxas PTFE 1985 shims to shim under the transfer gear but I think they’d be too thick on the output shaft side and result in binding. For those I’d recommend no thicker than 0.2mm and to check to make sure there is still endplay and you’re not preloading the shaft assembly.

Arrma Shims
Traxxas 1985 PTFE shims

If you picked up this Yokomo shim set you could do it all plus have a better selection to fine tune endplay.

I hope this helps out anybody like me that’s tried everything but still had the clicking. Le me know if you have any questions and if you try it out and are successful.

[Gramps]

Glad you found a solution for your clicking issue and thanks for sharing the solution with the rest of us. I just built the Chassis kit and don't think I have the same issue but I'm going to listen to mine a little closer.

[Benp]

Awesome video!!!!

Thanks!

I too have the clicking and it is on my to do list.

[Forker45]

Originally Posted by Benp

Awesome video!!!!

Thanks!

I too have the clicking and it is on my to do list.

Yes sir! I saw your thread on the clicking and tried all the suggestions there, but nothing worked on my truck. I’d be interested to see if your truck has the same issue as mine when you get to it.

[20vmki]

Great video and explanation, this is going on my to-do list for sure!

[Benp]

Originally Posted by Forker45

Yes sir! I saw your thread on the clicking and tried all the suggestions there, but nothing worked on my truck. I’d be interested to see if your truck has the same issue as mine when you get to it.

Still haven’t gotten around to it.

But the clicking went away after I put a HH Revolver 2500kv motor in.

All I hear is that

[Forker45]

Originally Posted by 20vmki

Great video and explanation, this is going on my to-do list for sure!

Thanks! Let me know if you need help or if you get it done and your results.

Originally Posted by Benp

Still haven’t gotten around to it.

But the clicking went away after I put a HH Revolver 2500kv motor in.

All I hear is that

Haha I’ve heard those guys are loud.

[Hubertrx]

Hello All,

I initially created an account just thank Forker45 for investigating this TRX4 click, and posting such a great tutorial on how to fix it! Thank you.
I carried out all the steps, there is no more play on the transmission shafts, and it significantly reduced the clicking.

Unfortunately the tick isn't gone completely. I suspect it's something to do with the driveshafts. I checked the phase/alignment, which is ok. I also lubed everything with dry lube. None of the set screws are sticking out.
My TRX is experiencing the same driveshaft rubbing against the transmission housing as mentioned in the below thread, however (with the set screws in correctly) I fail to see how this would produce a ticking noise necessarily?

Anyone else hate the driveshafts?

It seems to be worse AFTER going at high speed in second gear, or when reversing. It is a "rotating tick", and seems to match driveshaft speeds.

Does anybody have any more ideas please?

[Hubertrx]

Hello All,

Even though I didn't get a reply to my previous message, I kept investigating this annoying clicking. I just want to post my findings, for other people browsing the internet for a solution.

It turns out the original poster is absolutely correct.
Keep in mind that my TRX4 is NOT a sport like the OP, but a standard TRX4 with a high and low gear.

I used a slippery ramp as a test bench to create load on the truck, without it actually moving forward. This way it's much easier to pinpoint the sound. I then removed the driveshafts one by one, and conducted the same test.

Pinpointed the sound to the rear driveshaft in the transfer case, and another one somewhere in the transmission case towards the rear.

Opened everything up again (getting quite skilled at this now, can have the tranny open and back in 10 minutes) for inspection. Found more excessive clearances on several shafts as encountered by the OP on the output assembly.

Ended up shimming (in addition the OP advised locations):
- 0.5mm between 8293 input gear and transmission bearing
- 0.75mm (Seriously Traxxas!?) between pin 8293 and the transfer case bearing to the forward driveshaft
- 0.25mm between gear 8285 and the transfer case bearing to the rear driveshaft


So don't waste money on MIP driveshafts and aluminium transmission/transfer cases just yet, but take an hour or two, and follow the OP's advise: Buy the Yokomo shim set as advised by the OP, and just have a shim extravaganza in the gearbox.
If you still want to upgrade after that (I will, I still don't like the original driveshafts with the rubbing etc), go for it.

Thank you Forker45! You have saved my love for my TRX4..

[Forker45]

Hubertrx- sorry you didn’t get a reply to your first post, but I’m really glad you took the time to follow up with your final solution. Great post!

[DrIsotope]

As a longtime Traxxas owner, I always have a supply of M5x0.1mm shims on hand (McMaster part# 98055A095.). Traxxas teflon shims are nice, but sometimes it needs just that tiny little bit.