TRXultra4 Build

[XD60]

It started out as a roller of a bronco rtr I got off ebay. I paired it with some proline flatrions and some beadlocks ooff AliExpress.

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[bbrigg]

Originally Posted by XD60

It started out as a roller of a bronco rtr I got off ebay. I paired it with some proline flatrions and some beadlocks ooff AliExpress.

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Looks like a good start. I like the wheels and the Flatiron, they look good together. Two things caught my eye. The Mamba X sitting up front might help a bit with weight distribution but I would probably have used a stubby forward mounted battery which puts even more weight forward. Of course if you want to go with a big battery then the forward mounted ESC makes sense. The second thing is the lack of body posts. Did the chassis not come with them?

[XD60]

I always wanted to do a ultra 4 build with the TRX 4 just because of its combination of great durability, the 2 speed plus locking diffs made it perfect for higher speed stuff. Stripped down the truck taking off the fenders, battery tray, servo mounts and threw on some upgrades like the portal boxes and c hubs. I went with a yeti roll cage for the "ultra4" looks. I also changed out the springs and shock oils, and along with the new shock towers, I lowered the ride height to get an over all lower cg. It runs a mostly droop and a little spring set up. I also began designing sliders/boats sides that the cage would fit onto, replacing the stock plastic ones


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[bbrigg]

The second post just answered my two remarks. Looks good. The Yeti cage could have been meant to be there.

[XD60]

Surgery time!
First up the chassis was shortened. I actually kept the shock tower on the bronco wheel base position but ran with the defender links (12. instead, this laid the shocks down about which allowed for a less springy and even droopier rear end.

I made paper templates for all the parts i wanted to add, lots of measuring and wet throught about 5 versions before I was satisfied. My material of choice was 14ga stainless sheet, a bit on the heavy side, but plenty of durability, which was needed for the ultra4 style. The sliders are just bolted on using the screws the held the centre skid in place. The front skid was done to match the front end of the cage and is tucked up and out the way for better nose clearance.

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[XD60]

Originally Posted by bbrigg

The second post just answered my two remarks. Looks good. The Yeti cage could have been meant to be there.

Yeah, sorry this is more like a recount than a build log, the truck is completed already. Though I still appreciate the feedback!

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[XD60]

Lowering the CG:

It is well known that the TRX 4 has a pretty poor patter placement that when combined with the portal made for a top heavy truck.

My goal was to get everything as low and as centred (within the rails) as possible so it would be more balanced. The esc was moved up front as there wasn't much space for a battery with the pinch that the yeti cage has. I attempted to get the bettry as low as possible, which meant butting it up against the transfer case as that was the lowest and most centred point.

This became quite of an operation, much more complex than I have initially thought. I had to relocate no the 2 speed servo and the differ servos for this to happen. The 2 speed servo was moved forward and I managed to just heat up and bend the little stock shifter hook to make it work with it's new position. And the diff servos are kinda just hanging about and not hard mounted.

Honestly after all of that, Im still not sure if it's worth it but I could finally go out and run it at least. It ran really smooth and both the 2 speed and diff lockers ran as well as stock, so I'd call that a win at least.

Its running a mamba x and a holmes puller pro 3500kv on a flueron 2200 mAh 3s. The servo is a blue bird 50kg brushless HV. But I was stuck to only 6v on the BEC as the shifter servos couldn't take the 8.4v that the steering servo could.

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[XD60]

Here are some shots if it out running.

There is on small modification I did, I added a trim on the edge of the boatsides to keep the cage from shifting around while running. The trim just a small bent piece of stainless sheet which I spot welded to the boatsides.

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[XD60]

I finally got my first breakage about 2 months in, honestly I'm not even mad. I got distracted by a friend and went full speed into a rock pile. The truck tops about at about 30~35mph. It snapped the axle housing and the front half shafts, nothing else broke surprisingly, kudos to Traxxas for making such a tough truck. After swapping out a few inexpensive plastic parts, I was up and running again.

Here are just some detail of the rock rash. The lower links are actually kinda bent up but they still work so i just left it.

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[XD60]

And fastfoward to quarantine, I finally started working in the panels and interior of the tuck rather than going out running it.

Got a axial yeti interior and ordered up a 1/16" piece of lexan from Amazon and got to work

Again, the body panels were first mocked up with paper. I then traced it onto the lexan and cut everything out. I used a lighter the heat the panels to put bends in them. The rest is pretty self-explanatory, a quick paint job and some decals to finish it off.

At this point I also swapped over to a JX 46kg brushless 12v servo running straight off the 3s lipo. It'll most likely be swapped out later on as it really is lacking in power, I doubt there's 46kg. Hopefully I can get a reefs 777 someday.

Oh and the beadlocks rings, I swapped them out for some silver ones to match the body.

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[Steve g]

That is a great set up. Is the 2 speed even necessary? I only ask for durability, although since you haven't had issues with it, I'll assume it's as tough as the rest of the truck, and plenty strong. I really like the U4 style rigs, and you've got a perfect match of the traxxas durable base with axial cage looks.

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[rob5059]

That is a nice looking truck. You did a nice job cutting and bending up the sliders.

[themountain]

Originally Posted by XD60

Hopefully I can get a reefs 777 someday.

Awesome build ...but a reefs servo ?? Are you serious ??

[XD60]

Originally Posted by Steve g

That is a great set up. Is the 2 speed even necessary? I only ask for durability, although since you haven't had issues with it, I'll assume it's as tough as the rest of the truck, and plenty strong. I really like the U4 style rigs, and you've got a perfect match of the traxxas durable base with axial cage looks.

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Well strictly for crawling no, but the TRX 2speed is nice to have when you get to an open field, you can open up and bash around. The gearing between the hi and lo gear are actually wide enough that it's very noticeable and usable, much wider the scx10ii or the axial ones. I usually run a 9t pinion to get a smoother torquier low end and I think the final drive ratio is something stupid like 60:1 which is just so amazing.

Ive had any problem with the micro servos so far. I already have some spare metal geared ones from JX just in case. The Traxxas upgraded ones are just a plain rip off imo. just check the shifter servos' trim and end points from time to time to make sure they're not buzzing or fighting.



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[XD60]

Another mod I did and highly recommend is taking out some of the seal of the bearing in the transmission, obviously only take out the ones that are internal. This should be done straight out of the box, it take a bunch of resistance out of the drivetrain, take strain off the electronics and you also get a little more runtime.

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[TheseusOfTroezen]

Fantastic build, looks amazing!

I've seen that seal trick a couple times now. Wish I would have known about it when I put my TRX-4 kit together. Ohh well, just another thing to add to "the list".

[Bulldog]

Damn! I'm really diggin this! I've got a beater yeti chassis and a couple trx4 chassis and drivetrain setups. If I ever get back to building again, I'm definitely going to whip something up. I did a 1.9 yeti bomber project that was along the same lines, but I think I like this better! Any running videos? Youtube or instagram handle?

[AnimalHippie]

This thing is awesome brother!!! Really like it allot!!! Trx-4 drivetrain is a nice durable setup. I've been planning on doing the bearing seal mod on mine the next time I have the trans opened up. Keep up the great work!

[Inspector86]

That is cool. Nice work!

[size does matter]

I have a extra chassis. I’m for sure looking into doing this. I was just complaining about the body being heavy. I will just get rid of the body.