Father/Son TRX4 Sport Kit Build

[Forker45]

Due to quarantine shutting down the local race track I decided to jump into crawlers with my 8yo son for playing around the house. I chose the Sport Kit for the value and I also had all the electronics to get it going.

I knew the tires came unglued so I picked up some cheap beadlocks from Amazon.





The build went very smooth and the instructions were good enough that my boy could do a lot of it on his own.

We used some paint we had already. Tamiya PS-17 Metallic Green and PS-9 Gunmetal Gray.



Electronics I used from the parts bin:
Radio - Tactic TTX300 Tx/Rx
ESC - HW Quicrun 1060
Motor - HPI Gt550
Servo - DS3218 20kg



Right out of the box we were amazed at how capable the truck was on the wood pile out back. The HPI motor did pretty good and I even had a 16T pinion to gear it down a tad just after our initial running. The motor would run pretty hot and I figured it was tired (spent its former life in a hopped up powerwheels in my sons younger days) But I realize now that a lot of the heat and poor run time was due to it being standard rotation.
I didn’t want to be dead in the water if we let all the smoke out of the HPI so I ordered a Holmes Hobbies 550 Crawlmaster Sport 15T. Once I tried that guy out the HPI was put back in the parts bin! Amazing how strong it is, stays cool, and has great runtimes.

[Inspector86]

As you play with the TRX4 more you will find it is a very robust truck.

[Forker45]

Originally Posted by Inspector86

As you play with the TRX4 more you will find it is a very robust truck.

Coming from Arrma 1/8 6S and Mugen 1/8 race kits I could definitely see that during the build. All the plastics, gears, rod ends, fit/finish, etc...

One thing I did notice was the shocks were pretty much locked up as assembled out of the bag. I loosened up the bottom cap, hit them all with green slime filled them and snugged the caps up but they still just weren’t as smooth as I expect, based on experience. I noticed the suspension would even be stuck after sitting and have be “break-free” for travel. Clearly not ideal.

I searched through the forum & internet and found several topics on how to address the issue that were good reference.

Stock shock tuning / lower cap mod.
Has anyone rebuilt their shocks yet?
TRX-4 kit version shocks
shocks became very sticky after oil change

I also found Traxxas suggested info
https://m.traxxas.com/news/gts-shock-pro-build

A common theme was leaving the cap loose to free up the shaft movement but I wasn't crazy about that. I took some measurements of the x rings, spacer, & shock body. I found the spacer height for best xring compression to be 1.7mm where the stock spacer is 2.65mm. I sanded all the spacers down to this height and reassembled. Now the shocks are smooth as butter and no leaking.

[splyn]

interesting find. my rear shocks were binding badly. i changed the rear shock oil to 10wt after disassembling and lubing with motorcycle fork seal grease (i had some laying around) and discovered leaving the lower cap slightly loose was a huge improvement. now i think the 10wt is too light. will probably try 20.

[Forker45]

Originally Posted by splyn

interesting find. my rear shocks were binding badly. i changed the rear shock oil to 10wt after disassembling and lubing with motorcycle fork seal grease (i had some laying around) and discovered leaving the lower cap slightly loose was a huge improvement. now i think the 10wt is too light. will probably try 20.

Yes, leaving to lower cap loose is reducing the compression of the seals, which reduces friction on the shaft. For me just reducing the overall height of the seal-spacer-seal to be just slightly over the depth in the shock body makes more sense. I don’t have to worry about dirt buildup in that gap or the cap doming loose.

[Forker45]

I didn’t plan on modding this truck...but it’s been so fun I figured a couple things couldn’t hurt. 😂 I picked up some SSD portal weights, MIP HD Driveshafts, another set of Amazon beadlocks, & some RC4WD Boggers.

[Forker45]

The SSD portals were an easy swap and made a big difference in performance on the wood pile in the back yard.

[Forker45]

I went with MIP driveshafts because I’ve noticed a clicking noise when the truck is climbing under a load. It’s done it since day one and isn’t terrible like the trans is eating itself up, but I wanted to see what could be done. I did confirm the driveshafts were synced properly (I also was pretty sure they were since the instructions call it out specifically). From my forum searching it seemed like some guys were able eliminate the clicking by going to the MIP shafts.

Also, one thing I didn’t like was how the center spline section of the Traxxas shafts for my truck don’t slide freely within the yoke ends...actually getting stuck in one or the other. I was thinking this binding during axle travel could be contributing to the noise by affecting the axle pinion location/clearance during suspension cycling.

Unfortunately the clicking didn't go away on my rig so I have some more investigating to do. But overall I am extremely happy with the quality and smooth slip action of the MIP shafts. They were easy to build & install plus came with spare hardware. 👍🏽

[Timmahh]

I understand the axial scx10 iii has a clicking sound also. I say it's normal for a jeep or a ford to have lifter tick. lol

may be a wheel pin sliding around in the hex or maybe a gear the wrong direction in the trans? just tossing that against the wall to see if anything sticks.

sounds like the 2 of you are having a blast!!!

[Forker45]

Originally Posted by Timmahh

I understand the axial scx10 iii has a clicking sound also. I say it's normal for a jeep or a ford to have lifter tick. lol

may be a wheel pin sliding around in the hex or maybe a gear the wrong direction in the trans? just tossing that against the wall to see if anything sticks.

sounds like the 2 of you are having a blast!!!

Haha yeah a little tick never hurt anybody! The noise has been there from the start so I don’t see it as a damage/wear concern but just an NVH annoyance for me personally. I’ve also found a couple posts where guys eliminate it by changing out the motor mount setup. That’s probably the only other dislike I have as far as engineering/design of the truck. Even with the motor plate mounted there’s still movement which obviously will affect the pinion/spur mesh and could contribute to noise.

I checked all the usual suspects (set screws, wheel hexes, CVS, pinion grub screw, etc..) and didn’t notice anything with the transmission or axle ring & pinion during the build. I have a troubleshooting plan I will go through with my son so ’m sure I will find the source. It will be a good learning experience for him.

[Forker45]

When I got home today I did a little more digging on the forum and saw one more thing regarding the transmission clicking. I saw guys mention driveshaft phase as well as the input & output phase should match.
Transmission clicking
I went back through the manual and didn’t see anything in the trans build section specifically calling this out so it would be easy for the builder to overlook.

I checked our truck noticed the front and rear transmission outputs are just slightly out of phase...maybe this could be the source. I will try correcting this tomorrow and see if it works. 🤞🏼

[Forker45]

We also mounted up the RC4WD 1.9” Boggers Sunday on some bronze DJX beadlocks from Amazon. We picked out the Boggers because they look sweet of course, and to have an option for mud & trail running.

One observation is they run narrow, more than I would have liked to be honest. I would have gone with ProLine if they made them in 1.9 around the 4.75” TRX4 size but oh well. They are still a pretty soft compound compared to the Canyon Trails and the sidewall is much softer than I was expecting based on what I had read from people’s opinions on the forums. They are a bit taller as well.


They definitely don’t climb as well on the wood pile but they seemed to shine in the dirt and concrete climb on our culvert in the front yard. Plus they look cool and my boy likes them!

[Gramps]

Good looking rig, that is a cool green

[TheseusOfTroezen]

What beadlocks did you end up going with? I'm looking for an inexpensive set but a lot of what I found on amazon the reviews said they won't fit the TRX-4 with spacers.

[Forker45]

Originally Posted by TheseusOfTroezen

What beadlocks did you end up going with? I'm looking for an inexpensive set but a lot of what I found on amazon the reviews said they won't fit the TRX-4 with spacers.

Here’s a link to the beadlocks.
https://www.amazon.com/dp/B00UN714LO...p_mob_ap_share
I also have a gunmetal set in same style but they didn’t have the scale beadlock screws. The seller has several that fit TRX4 based on the reviews. I just made sure to pick a set that has SLW style hubs, so even if the offset wasn’t perfect I could correct it with some different hubs.

[Forker45]

Well I took the trans out tonight and matched up the phasing on the input & output shafts but that didn’t fix the clicking. I ran it upside down and confirmed there’s little to no noticeable noise under no load but it is there when I apply drag to one of the driveshafts. The sound matches the driveshaft rpm and seems to be in the trans based on sound/feel but I don’t think I’m going to spend much more time chasing it.

[Forker45]

The RC4WD Bogger performance has been pretty lackluster so I decided to cut them. The Canyon Trails have performed great everywhere I’ve tried them so far. I think one key factor is their lug spacing, which is just about even with every other lug on the Boggers.



I used lexan scissors and snipped all the small lugs off.





We tested them out on the wood pile and the performance was much better! The wider lug spacing was just what they needed and I expect the performance in all other conditions (sand, loose dirt, mud, etc...) to be just as good. I may even sipe them sometime later similar to how I’ve seen guys cut 1:1 Boggers.

[Forker45]

Well the Boggers look cool but just don’t perform as we hoped. So I pulled them off the beadlocks and put them on the TRX4 Sport wheels.





I ordered a set of Proline Krawlers in G8 compound to go on the beadlocks when they arrive.

[20vmki]

I also have a slight ticking, trying to talk myself into being okay with it and that I don't need to take the whole thing apart to troubleshoot!

[Forker45]

Originally Posted by 20vmki

I also have a slight ticking, trying to talk myself into being okay with it and that I don't need to take the whole thing apart to troubleshoot!

I fixed the clicking / ticking sound that I had by shimming the transmission. Check out the thread for more details and a video I uploaded to YouTube.
Transmission Clicking Fix