CoolRunning's simple TRX-4 mods

[CoolRunning]

Thought I'd add a simple mod thread. Nothing fancy as I'm not doing anything radical. Why am I doing this when nothing has failed or played up? Simply because I feel like it. I imagine things would have worked fine for the next few months until the weather warms up anyway but it's something to tinker with when the weather outside is lowsy.

I've added some strip LED lights to the front and rear light buckets which work great (I'll add some info and pictures soon). I've also removed the rear tyre and filled my bumper with lead (I've posted about this previously - pics also to come) which made a huge difference to the truck.

I'm now embarking on some new mods as I've just received:

- Savox 1210SG waterproof 277oz/in @ 6v servo

- Hobbywing WP 80 (1080) amp waterproof 3S ESC (bargain ESC at $45AUD - about $32USD - crazy cheap).

I'm also:

- Installing the stock Traxxas steering servo as a shift servo

- Changing the RX box as I detest it (too big, difficult to get at the cables and it's a HUGE pain...seriously huge...if you use silicone on it to make sure it stays waterproof ).

- Removing the rear locker servo and going to attempt to 'lock' the rear diff using 'shims' inside the rear diff. Whilst I'm at it I'm going to open everything up and see how everything is going as I've had a few water outings in creeks.

Some notes...

Some things in the truck are a fair PITA to get at. This is no SCX10.1 in regards to ease of access and simplicity!!!

Micro shift servo mount removal requires you to remove:

- battery mount
- motor cover
- motor
- trans
- shift servo
- servo
- TX box needs to be opened and the rats nest of wires navigated.

You cannot easily install a larger servo without removing this piece.

Here is a pic of my mockup with the full sized servo. It's going to fit well and likely will shift perfectly from initial tests. No buzzing or annoyances with initial testing and full throw shifts.

I'm using the stock servo saver, and SCX10.1 servo mount and a piece of aluminium plate which I'm going to 3M tape to the running board with a couple of screws to firmly anchor it. I don't think it's going to need radically locking down.

I will then have two spare servos for the front diff locker for future failures. 3 servos should keep it going for a fair while indeed (no plans for adding a full sized servo for shifts atm though once all the micros are dead, I'll make the change).

[CoolRunning]

I can confirm that the servo mod works a treat. It was simple making up the plate and aligning it (just took a little care) and it shifts perfectly every time. You can hear it shifts with far more authority with 4 times the torque of the tiddler micro servo. Now if I ever have an issue, I can easily get another waterproof servo for the price of the micro without any hunting around...actually I have a Tactic from my SCX10 that I could use if the Traxxas unit ever conks out.

For all you blokes that have replaced the steering servo, you have a perfectly good unit for shift duties right there. Then you have a spare micro for when one of the others packs it in.

The Savox 1210SG works WAY better than the stocker. It might be only just over twice the torque of the stocker but it feels like 3 times. I added a TLR style aluminium horn which works pretty well.

Now to the HW WP80.

Firstly, I want to say that it immediately ran cooler. Surprisingly it seemed to have better resolution and low speed control plus the drag brake seems better. The truck just seems to crawl better with it installed. I though the Traxxas ESC was pretty solid apart from getting a tad warm but here the cheap little $32USD Hobbywing comes along with a BEC that powers two full sized and a micro servo without a cap, runs cool, seems smoother and crawls better and the drag brake seems a bit better to boot. Love the HW (I have 3 now).

I just have to sort out the RX box. I've decided for the time being to just run all the wires through the hole in the top and silicone it up. It'll be simple and will be easy to open up if I need to. I doubt any water will get in like this.

Oh yeah, I pulled the rear locker servo and pulled the rear diff apart to lock it. I've been playing submarine a fair bit and everything looked fine inside. The grease was a little watery but it was still doing a good job.

I ended up putting in a thick plastic shim and a thin metal spacer which was about perfect to take up the space where the diff lock used to move. The truck now handles far better. It's gone from barge to nippy. I love the idea of open front diff with locked rear or full locking. Now that is how it should have come. I have no use for all open diffs myself.

I forgot. I also installed a rear MIP driveshaft as I had one from my LWB SCX10.1 as I had to shorten the front driveshaft with the SSD 2 speed so it no longer fit. It fits perfectly in the rear of the TRX4 and was a lot smoother and nicer than the stock driveshaft. I now have some driveshaft spares for the front, plus the 2 spare locker servos, a locker cable/c clip and servo saver.

[Frank211]

Does the MIP rub on the skidplate , or is there any clearance/gap between the shaft and skidplate?

[CoolRunning]

My particular LWB 313mm set MIP does not rub and fits perfectly. Clearance is about 1mm and it's like it was made for the rear.

Update: I'm surprised but my TRX4 now crawls far better. The slow crawl is loads more consistent and the slowest creep is slower and much less jerky; it so smooth now. Drag brake and mixed super slow creep over and down a rock is way better. It makes me look like a better driver! Lol

Motor seems to run slightly cooler which is unusual. ESC was ambient temp yesterday where the stocker was never cold.

I have found the TLR sized horn I picked up and the Savox really powerful. I think part of the issue with the stock servo is the horn is very long. The extra length which clears the panhard rod dilutes the servos turning power.

I think the reason my modest Savox feels so powerful is that my horn is also shorter. The downside with a short horn is that you must reset end points (simple) which gives you less steering throw to the left to stop binding. I may pickup another longer horn down the track though I'll see. Steering is still fantastic to the right and decent to the left for the moment.

Also, locking the rear permanently has made a considerable difference to how the truck handles.

Locked rear and open front now can do doughnuts and zoom around without rolling over or flopping around like a barge with the powered wheels loosing and gaining traction in an annoying cycle of wallow and grip (which I found frustrating and no fun).

Shifting is now FAR more authoritative and likely worlds more reliable. I pulled the front diff lock and dismantled things for grease and IMO the stock servo is clearly very underpowered for the job. It sounds like it's struggling. I agree with the poster that felt it needs about 70 oz/in of torque to lock/unlock well.

I'm extremely happy with how my simple mods have come out.

[wrightcs77]

Nice work. Sounds like the mods work well

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[Mudflap84]

That's my next mod Coolrunnigs. I was correct about the Bluebird 373mg's - not enough torque to survive. The rear one overheated and quit after 2 packs. The rear diff will stay permanently locked from now on.I'm going to keep the front operational, but as I said it's going to take something in the 70in/oz + range to be dependable. I think building the new servo mount and retaining the cable lock should be pretty straightforward. I don't think some realize the effort it takes lock and unlock these diffs. This change will make my fourth servo purchase for this thingamajigger. Hopefully the steer servo won't finally fail handling the two speed duties but I'm not optimistic. Change that number to five-gonna buy 2 and hopefully be done for good. Pay attention Traxxas:this is a big problem and I think you already know


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[CoolRunning]

I think you're on the money with 70 oz/in. I think it's compounded when the little servos get a bit hot and start weakening. Then they really start struggling. Mine sounds a bit ill already and went from working fine to audibly slower (it makes that under pressure sound).

How do you think you might mount the diff lock servo?

I've moved my receiver box now to a somewhat odd though functional L piece so I've effectively got it standing vertically suspended above the running board so I now have room on the running board for a full sized servo. I wanted a clear RX box so I can see if water gets in and found some quite small watertight snack boxes for $2.50 for 3 of them which seems to work great. They don't look fancy but are super easy to open (4 catches) and I can see when a seal fails unlike all my other trucks (where I have to cringe when something starts glitching).

I have a couple of screw down servo mounts so I figured I could do what I did with the shift servo and have one lying down and cut the cable mount so I basically screw the top square bit onto the aluminium plate next to the servo horn with effectively the same distance and angle as current though with a much more powerful servo lying down.

I've pondered standing it up and I could easily make another L mount for it but I wonder if it's easier (at least for me to fashion) laid down.

What do you think you might do?

Originally Posted by Mudflap84

That's my next mod Coolrunnigs. I was correct about the Bluebird 373mg's - not enough torque to survive. The rear one overheated and quit after 2 packs. The rear diff will stay permanently locked from now on.I'm going to keep the front operational, but as I said it's going to take something in the 70in/oz + range to be dependable. I think building the new servo mount and retaining the cable lock should be pretty straightforward. I don't think some realize the effort it takes lock and unlock these diffs. This change will make my fourth servo purchase for this thingamajigger. Hopefully the steer servo won't finally fail handling the two speed duties but I'm not optimistic. Change that number to five-gonna buy 2 and hopefully be done for good. Pay attention Traxxas:this is a big problem and I think you already know


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[clm]

You could always cut up the diff lock mount, have one end come in higher then the other and have one servo with a double arm work both locks at the same time, one cable going to each side of the servo arm.

[Vedo]

Originally Posted by CoolRunning

I can confirm that the servo mod works a treat. It was simple making up the plate and aligning it (just took a little care) and it shifts perfectly every time. You can hear it shifts with far more authority with 4 times the torque of the tiddler micro servo. Now if I ever have an issue, I can easily get another waterproof servo for the price of the micro without any hunting around...actually I have a Tactic from my SCX10 that I could use if the Traxxas unit ever conks out.

.

I just did this mod and am trying to get the linkage to go full throw. Mine seems to pull then "pop in" when I start to move. Is that just normal gear engaging? https://streamable.com/8umie

[magic_yeti]

Originally Posted by Vedo

I just did this mod and am trying to get the linkage to go full throw. Mine seems to pull then "pop in" when I start to move. Is that just normal gear engaging? https://streamable.com/8umie

you should only shift if the trucks is slow moving and yes if you shift if it's not moving it's normal.

[Vedo]

Thanks. I never shift while moving =) Good to know it's alright

[Meatwad]

The trans can take it. Full throttle shifting with a castle slate motor... for the other stuff down the line only time will tell.