1/10 4WD build

[95PGTTech]

The XO-1 is the same diff. As a 100mph 1/7 scale does that mean it has crappy 1/10 MT diffs or does it mean Traxxas 1/10 MT diffs are that robust/capable? They even use the same case. Both are two planetary gear setups/one shaft. The other two are the sun gears. This is how the ECX 2wd is, how most RC diffs seem to be, and how most 1:1 stuff is. As opposed to the ECX 4wd stock diff, which has 4 planetaries and 2 subs. I can’t access the old thread linked on ECX 4wd diff failures, any chance anyone remembers what in particular failed about them? Hopefully not the housing or the case LOL looks like those must be reused.

Losi diff internals arrived. They are close, but not in any way the same. In each of these pics the screwdriver indicates the ECX part. Different diameters on sun and planetary gears. Different pin lengths. Different depth on planetaries. Different pin setup for planetary to outdrive.

Some more Traxxas parts arrived to explore swapping the entire Traxxas diff/ring/pinion into the ECX housing. This would absolutely require front and rear be done as it would change the gear ratio (39T ECX ring, 37T Traxxas). Both 13T pinion. Pinion of Traxxas same shaft diameter but single piece probably would require custom center driveshaft.

Ring diameter 38mm ECX 37.5mm Traxxas
Diff width out to our 31.40 ECX 32.08mm Traxxas
Bearing journals (for diff bearing ID) 12, 12 ECX 8, 10 Traxxas. ECX diff housing has two 18mm journals for bearing OD


Some pics of my Traxxas guts in ECX diff installed in a ECX housing. I only had one 12x18 bearing on hand. Next pics of Traxxas diff in same housing. I think this is as far as we go before killing the idea. Pinion too far into housing to attach anything to its end for the center driveshaft. Diff too wide for housing are first major hurdles. No way to shim it for R/P mesh.

We tried. I guess a backup idea for now is if I can’t get the Traxxas spider gears to work well in an ECX diff, just put the Traxxas out drives in it and weld it as a spool. Not ideal, but not unheard of either. Better than a permanent 3WD shelf queen

 

[slick2500]

The Traxxas “supercar? Sorry I’m such a newb these two Ruckus are literally my first RC ever I want to make sure I’m looking at the right thing. I hadn’t even considered looking at non-trucks

https://www.astramodel.cz/en/eview/traxxas-6407-xo-1-7/front.html

I swear I saw someone post that they put 4 gear diffs out of the XO-1 into their Stampede 4x4. But I cannot seem to find a 4 gear diff for the XO-1.

 

[slick2500]

The XO-1 is the same diff. As a 100mph 1/7 scale does that mean it has crappy 1/10 MT diffs or does it mean Traxxas 1/10 MT diffs are that robust/capable? They even use the same case. Both are two planetary gear setups/one shaft. The other two are the sun gears. This is how the ECX 2wd is, how most RC diffs seem to be, and how most 1:1 stuff is. As opposed to the ECX 4wd stock diff, which has 4 planetaries and 2 subs. I can’t access the old thread linked on ECX 4wd diff failures, any chance anyone remembers what in particular failed about them? Hopefully not the housing or the case LOL looks like those must be reused.

Losi diff internals arrived. They are close, but not in any way the same. In each of these pics the screwdriver indicates the ECX part. Different diameters on sun and planetary gears. Different pin lengths. Different depth on planetaries. Different pin setup for planetary to outdrive.

Some more Traxxas parts arrived to explore swapping the entire Traxxas diff/ring/pinion into the ECX housing. This would absolutely require front and rear be done as it would change the gear ratio (39T ECX ring, 37T Traxxas). Both 13T pinion. Pinion of Traxxas same shaft diameter but single piece probably would require custom center driveshaft.

Ring diameter 38mm ECX 37.5mm Traxxas
Diff width out to our 31.40 ECX 32.08mm Traxxas
Bearing journals (for diff bearing ID) 12, 12 ECX 8, 10 Traxxas. ECX diff housing has two 18mm journals for bearing OD


Some pics of my Traxxas guts in ECX diff installed in a ECX housing. I only had one 12x18 bearing on hand. Next pics of Traxxas diff in same housing. I think this is as far as we go before killing the idea. Pinion too far into housing to attach anything to its end for the center driveshaft. Diff too wide for housing are first major hurdles. No way to shim it for R/P mesh.

We tried. I guess a backup idea for now is if I can’t get the Traxxas spider gears to work well in an ECX diff, just put the Traxxas out drives in it and weld it as a spool. Not ideal, but not unheard of either. Better than a permanent 3WD shelf queen

View attachment 7865View attachment 7866

He must have meant these https://traxxas.com/products/parts/5379R https://traxxas.com/products/parts/6879R
But those won't help you.

The last time I looked at that thread was back in 2017 and I think it had something to do with the screws working loose and the crown gear separating from the cup.

 

[95PGTTech]

I swear I saw someone post that they put 4 gear diffs out of the XO-1 into their Stampede 4x4. But I cannot seem to find a 4 gear diff for the XO-1.

This is the only thing I can find on the XO-1. They use an identical picture for the rear diff. For what I’m doing I’m not too hellbent on it - the extra planetary gears (or spider gears for those that use that terminology) help the differential transfer power with less twisting loss, smoother, and help it function more like a LSD. Why these guys can’t make an aftermarket hardened “pumpkin” with a simple wave spring like a Ford LSD (or many other OEM manufacturers, Detroit TruTrack, etc is beyond me. The space is there.

Thanks for the intel on the ECX stuff. As always, your help is very much appreciated. Another pothole to look out for.

 

[95PGTTech]

He must have meant these https://traxxas.com/products/parts/5379R https://traxxas.com/products/parts/6879R
But those won't help you.

The last time I looked at that thread was back in 2017 and I think it had something to do with the screws working loose and the crown gear separating from the cup.

The 6879R uses the style pinion ECX uses. Any chance you remember what Traxxas model you found that came off of?

Edit: it’s for the rear diff. They use different pinion setups front and rear. What an absolute waste of time and resources you can’t make this stuff up. Ordered a 6879 for fitment. For other newbs like me add R to the end of those diff numbers for the upgraded helical cut gearset same ratio.

 

[slick2500]

The 6879R uses the style pinion ECX uses. Any chance you remember what Traxxas model you found that came off of?

Edit: it’s for the rear diff. They use different pinion setups front and rear. What an absolute waste of time and resources you can’t make this stuff up. Ordered a 6879 for fitment. For other newbs like me add R to the end of those diff numbers for the upgraded helical cut gearset same ratio.

I have a Slashpede 4x4 and I thought that was the weirdest thing ever.

 

[95PGTTech]

Just a quick follow up on the 6879 next to the ECX ring and pinion. Not going to work, it won’t allow a bearing on it that will still fit in the ECX housing. So Traxxas diff guts may work in a ECX diff but a Traxxas complete diff won’t work in an ECX case. Maybe somebody out there has the skill to 3d print a housing that uses the Traxxas internals but keeps the ECX external mount points, but at that rate mind as well print the inside for a better aftermarket diff and R&P.



Got the 4WD down from the shelf, the axles are here and I have the time. Blew the front end apart and took some pics as I went. Notice the new witness mark on my center driveshaft? Still hitting the steering somehow.







Side by side shot with the Traxxas internals ECX diff. I superglued the ring gear bolts (the loctite of the plastic world) per another members warning. And now sitting here thinking about it, I’m not sure if I put final diff fluid in it. Oops.




Well, there you have it. The axles are hardened steel aftermarket double universals for a 1/10 slash 4x4 vxl. Those are actually the rears I caught the error after this pic. I run these axles in our 3s 3674 ruckus 2wd and absolutely love them

 

[95PGTTech]

So the elephant in the room is an axle has two ends…a differential (or trans) end and a spindle end. At the spindle, the inner bearing works fine. 10x15x4 is actually the slash inner too. The problem is the outer. ECX uses a 6x12x4 bearing and the axle is 5mm OD. The ECX spindle/steering knuckle/bearing holder whatever RC term of the week we are using is actually much deeper (put an ECX axle spindle next to a slash axle spindle you’ll see it’s much longer). So the hex pinhole doesn’t protrude out the end of the knuckle. I put those custom 10x15x3 bearings I had Boca make back in…helped, but not enough.



I kept it moving just using the stock outer bearings for now and a washer and figured out there still is enough spindle there and then threads that I can get a 5mm hex on it and still get a wheel and wheel nut on it at full thread.



Options:
1. Run a conversion bearing 5x12x4 and redrill for another axle pin
2. Swap to a different outer half (spindle side) axle from another model that fits this spindle better.
3. Put a different knuckle on it that fits the outer axle better

This afternoon I ordered up some bearings since they were common and after a lot of research the optional HD Slash 4x4 knuckles. I think those are the least invasive next steps. Got the tie rods too expecting the need for some adjustment.

 

[95PGTTech]

Working prototype

I can’t operate the drill and cycle the suspension in my state of the art video editing studio, you’ll just have to take my word that the center splined slip fit has far more range of motion than we need to work without binding. Steering lock to steering lock is okay too sorry for my fat hands.

It’s TIGHT to the huge GTR shocks at full lock but there is an air gap there. Something to keep an eye on. The weird S shaped suspension pieces that tie the upper and lower control arms together (loosely) will absolutely not clear and need to go. I’ve not seen them on another model nor understand what possible purpose they serve (despite being included in suspension replacement parts packages).



And now all we do is wait for more parts to come in. And prepare a lot of stuff to go back to Amazon LOL

 

[95PGTTech]

Chinesium slash 4x4 knuckles arrived the "heavy duty" option with the two arms for the tie rod. I like that there are a lot of companies out there that make these upgrades for a popular model like a slash so if these cheap test fit parts do work I can go order some actual quality stuff not "coda" or "hobbypark" or whatever we are calling generic drop shipped from China this week (as opposed to ECX stuff, where you have ECX brand factory upgrades which are basically as rare as dinosaur tears, H-R garbage, and RCAWD (our China parts) super hot garbage).

They LOOK similar, and the single most important detail is these fit the aftermarket slash 4x4 axles PERFECTLY using commonly sourced bearings nothing special order, but are different in some significant ways - the outer wheel bearing is 5x11x4. I had none of these, so ordered again. I did have some 6x11x4 which worked for mockup just fine.



How they attach to the steering is different - two versus one tabs is no big deal, but the geometry is very different - much shorter pivot points (from center of axle bearing) and located much more outboard of vehicle. Both of these problems were fixed with Traxxas 3741 turnbuckle kit that we were going to run anyway. I have it on our other Ruckus 2WD.



How they attach to control arm is different - m3 for traxxas m4 for ecx. a bushing will be needed. in my first pic in this post you can see a regular m3 was good enough for mockup.

This pic shows the overall height from the end of one mounting boss to the other (upper LCA to lower LCA for ECX and caster block to caster block for Traxxas). 32mm vs 26mm respectively. This presents an issue because in a double wishbone like the ECX you want the two control arms parallel to each other, so directly bolting the Traxxas knuckle spreads them out like a trapezoid.

Maybe these pics help better visualize that. Notice how the control arms appear to be further apart at the knuckle than they are at the chassis mounts. Also notice the amount of negative camber this setup would result in. Negative 7.5 installed as Traxxas designates them left and right. For you know whats and giggles I mounted them backward because of how the upper and lower bosses are offset and it actually got worse to almost negative 9 degrees and put some really weird geometry into the tie rods. With non-adjustable ECX front camber, -7.5 is a BIG problem.

The other pics are just various axle exposures out the axle, and the axle themselves. I have a 2wd axle on hand also, but I don't like the idea of it's smaller bearing sizes. So, as I see it:

1. I'm keeping the "redrill the axle pins" in my back pocket. the outer wheel bearings will be here tomorrow. this requires me to keep the custom 10x15x3 inner wheel bearings (for reference, a set cost $28 to have made). I need that custom bearing because I need all the extra thread I can get on the end of that axle going through the much deeper ECX knuckle. These ECX steering knuckles are $51 for a set and good luck finding any. I'm hoarding a backup pair.
2. go looking for that different outer axle section to work better with the ECX knuckle using the standard 10x15x4 bearing and not needing redrilling hopefully) to go with the inner section we have working now
3. give up on the traxxas knuckle entirely and find another knuckle. this is problematic because of the non adjustable camber (I can shim caster a bit).
4. continue down this path and find a different upper or lower control arm that will bring the camber to somewhere -1 to -3 range. bushings for the upper and lower "ball joints." have a machine shop take 6mm out of these knuckles to align the control arms again.



the knuckle has 3 parts right - axle, steering, suspension. with this slash 4x4 knuckle axle is totally sorted, steering is totally sorted with one part. with the ecx knuckle steering and suspension are sorted but axle isnt. back on amazon I was looking up various rc car upper and lower control arm lengths to figure out lengthening the upper or shortening the lower and I realized what I really need is an adjustable upper. that's really what did it on the steering, the ability to adjust the length of that traxxas turnbuckle. so I ordered up some traxxas slash 4x4 style lower control arms, caster blocks, all the hardware and bearings, and upper camber link. got the front shock tower too - screw it, prime, free returns (the camber link mounts to it in the slash).

 

[95PGTTech]

Bearings arrived. Conversion outer bearing to run the Traxxas axle in the ECX knuckle and stock Traxxas inner and outer.

1. ECX knuckle using OEM bearings and OEM dogbone=4mm shoulder protrudes, then 11mm more threads
2. ECX knuckle using OEM inner, conversion outer and steel CV axle = 5mm shoulder protrudes, 9 more threads
3. Traxxas knuckle, OEM Traxxas bearings, steel CV axle = 9mm shoulder protrudes, 9mm more threads

I didn't take a picture of option 2 I guess, but there is one in the previous post (keep in mind it's got the thinner custom 10x15x3 bearing in it though, so subtract 1mm of that axle protrusion out).


The first picture with the Traxxas setup is with a pin in the axle and a 0.1mm shim, just like it would be run on the truck. 8mm aluminum wheel hex. the ECX one has no pin in it (because it's too far in the knuckle), 5mm hex, and m4 nuts locked together for mockup so it can spin free. I would definetely not be comfortable running a 8mm wheel hex on that.

The whole Traxxas order should be here Monday, so Tuesday afternoon during naptimes I'll probably have a chance to tinker with it again. I'm keeping the "just redrill the aftermarket axles a new pin hole" option in my back pocket as a last resort...the less custom made parts, the better.

 

[95PGTTech]

I don’t have a ton of time to make a huge update, there were a ton of parts back and forth and measuring and what not but I believe we have a working prototype and accomplished our goal of all off the shelf parts with minimal modification (mostly for the ability to service it in the future) and GOD DAMN is it not a beautiful piece




This just may have saved our 4WD Ruckus from being a 3WD permanent shelf decoration.

 

[95PGTTech]

Double wall spacers finally came in for the new wheelie bar. Hopefully these hold up to the heat of MIG welding better.



Front suspension parts arrived. RPM lower arms. Only kind of aftermarket arms I will run. Unfortunately, dimensions I found online were wrong. I thought the inner mount was more narrow than the ECX arms...crap. That's a big problem considering how our control arm mounts, the front lower hinge pin brace won't fit and the pin is too short. I have 2wd front and rear on hand, neither are going to work.



I got to thinking. The smoke detectors went off in the house [dad joke]. The ECX arms are 3mm wider at the inner mount. What if I offset the front hinge pin 3mm forward, I have some m3 spacers meant for shocks. The only thing up there is the front bumper, seems it will clear.




the massive GTR shocks now hit the strut tower. 2mm spacer addressed that fine (next post down). I needed to rotate the lower perch too. For now the Traxxas turnbuckle is just set into the front shock tower where the old pin for the upper control arm went. The rear brace for that control arm (that bolted to that trapexoidal steering brace) is no longer needed. I explored the idea of keeping it and the pin and running a stock type triangulated upper control arm but could not find one that was adjustable. The Traxxas pieces being adjustable length (tie rod, upper control arm, and axle), are what really make a conversion like this possible. The only fixed length item is the RPM lower control arm.


"Coda Racing" caster blocks. More Chinesium pieces. Here for test fitment and to get beat up. Once everything is sorted, quality pieces will take their place (probably the Traxxas aluminum ones). Another cool, unexpected, feature, is the multiple upper mounting holes...this will allow me to correct the angles so the upper and lower control arms stay as parallel as possible through their suspension travel. The Traxxas turnbuckles provided plenty of adjustment for me to get the suspension to an eyeball zero toe zero camber starting point.

 

[95PGTTech]

I went back and put longer screws than stock in the front pin brace (I actually ended up going to stainless fine thread eventually, but you get the point).



All coming together now. Stuff like shock mounting position I really just picked a spot and we're going to have to run it and see.



Test fit the Traxxas front shock tower as it has multiple holes for the camber arm (upper control arm). Nowhere close. Kept pictures in case I do 3d print in the future, this may be a project. Our diff housing has a H shaped plastic piece that bolts to the top of it (it comes as part of the shock tower set and doesn't have a name in the manual). our tower bolts to it. it would be simple enough to 3d scan it and reprint a modified one to accept the Traxxas shock tower. This ECX aluminum one I have is another one of many unobtainable items I have on this thing. I think 3d printing is a cool avenue of modifying because it would allow the file to be sold/given to other members so they could just have it printed and make theirs a bolt on affair. A really cool more advanced project would be to 3d scan the entire diff housing and then reprint its internals to house different beefier aftermarket differentials so someone wouldn't have to go through everything I did to modify theirs they could just drop in an entire new differential assembly but keep the external dimensions and mount points.

For now, I drilled out the ECX hole that mounts the pin completely through to allow a nut/bolt. I would have preferred to drill it and tap it for m3, but the hole was already 3.0 for the pin and m3 needs a 2.5mm hole before tapping. I won't put too much of a knock on this for "having to modify parts" because I think everyone can grab a drill and finish a 3mm hole that's already there. While I was at it I enlarged the four mount holes for the shock tower to that H shaped piece to 3.0mm...the stock hardware was way too tight in there, ECX has some real issues with detail work on their aluminum pieces.

 

[95PGTTech]

We don’t have enough pics in this thread, we need more! Work from today...

Try as I might, not having to make or modify anything simply wasn't in the cards. The lower control arm pins measured 51.5mm. For mockup they were fine, but I really needed to get ones 3mm longer in there so they really fit into the front and rear brackets well. I went 54.4mm to give the tiniest bit of wiggle room. Ordered some 3mm stainless rod on Amazon and cut it down to size with my band saw and slowly took it down with the bench grinder.



Redcat Racing upper control arms arrived. There are very few length adjustable upper control arms out there, surprisingly. I didn't really think they would work, but again, Amazon Prime free returns why not. I take stuff out of the bag when it's a ziplock when I can reseal it and restaple it in a way that looks never opened for the next guy...I wouldn't want to receive some item that looked buggered up. I never intended on using the whole thing I was going to use just the inner part and the threaded middle, but the inner just doesn't fit the shock tower like I had hoped. If I go back to a pin style upper, it pushes the control arm really far backward. It's fine, the Traxxas caster block offers a lot more forward/backward stability to the knuckle than I thought. I figure it's just as important to document the fails as it is the wins.



Pretty excited to get this front end back on the vehicle and drive it around the house then take it outside and send it. I'm trying to think up some sort of environment I can run it and actually find stuff when it falls apart (my lawn, it's gone forever).

 

[95PGTTech]

Front end back on for the first time in awhile, driveshaft back in



Had to clearance the front bumper a little because of the pin bracket being pushed forward, nothing crazy



Worked on the steering a little too. The idler, the only thing that stays stock with the ECX aluminum steering kit, had a ton of play in it so I just made one. The stock one measured 60mm, I also tried 55mm because that's the distance between the two steering pivot points (to create a parallelogram) but for some geometry reason I can't figure out it wouldn't turn both wheels equally. I moved the main steering rod up a little to give the driveshaft more clearance

 

[95PGTTech]

Installed the spine with just enough bolts that I thought it was secure (there are like 16!) and a battery. Maiden voyage just real slow around the house. Crap out today. Everything seems to work okay, turns like a boat.




Here it is compared to the 2WD. I don't have a shot from before. The wheel hexes may be a factor there too (wide on the 2WD narrow on the 4WD right now). It's so odd to see them both sitting there ready to run at the same time. LOL!

 

[95PGTTech]

It saw the sun for the first time in a long time. Quick alignment. Just walked around it a lot with the body off doing figure 8s and uneven surfaces more of a crawl than a run. I think the GPS said the quickest we went was 10mph lol

I still am over the moon. Breaking that axle and finding out realistically this needed to be retired hurt a lot. We still need to see if it works under power, but even to get to this point feels like a small miracle.



A little under 70% seems to be the good endpoint on the radio where the steering arm doesn’t hit the center driveshaft. I could maybe space it up a little higher but I’m not sure how much more steering I would gain as the outer tie rods are already pretty close to hitting the wheels.







Somebody I think on here asked me what I mean about blowing out. What it looks like after a session vs five minutes (probably not even) of maintaining our equipment.

I’ve never enabled the GPS in the receiver before. I found out on our 2wd it needs to be mounted flat not on its side. Does a fine know if it has a specific orientation? DumboRC instructions are a bad bad translation and don’t say

 

[diamondjaydub]

This is pretty amazing "shade tree" engineering. Seems like you have it figured out at this point. Once you test will you be doing a final write up with the parts used? Very interested as I have an ECX 4wd Torment shelf queened over lack of parts. Also thinking about the center drive shaft - seems like one could be made out of steel rod somewhat easily? McMaster has "High Strength easy-to-machine 1144 Carbon Steel Rods" in 1/4" diameter by 12" lengths for $1.87 each. I wonder what a machine shop would charge to turn a few up?

https://www.mcmaster.com/steel-rods/high-strength-easy-to-machine-1144-carbon-steel-rods-8/

Jim

​

 

[95PGTTech]

This is pretty amazing "shade tree" engineering. Seems like you have it figured out at this point. Once you test will you be doing a final write up with the parts used? Very interested as I have an ECX 4wd Torment shelf queened over lack of parts. Also thinking about the center drive shaft - seems like one could be made out of steel rod somewhat easily? McMaster has "High Strength easy-to-machine 1144 Carbon Steel Rods" in 1/4" diameter by 12" lengths for $1.87 each. I wonder what a machine shop would charge to turn a few up?

https://www.mcmaster.com/steel-rods/high-strength-easy-to-machine-1144-carbon-steel-rods-8/

Jim

​

I lucked out on my center driveshaft when another member on here sent me a link to where 2 are left. I’m waiting to know my driveshaft to steering arm clearance is perfect before I put the virgin one in. After I finish the rear end, I’d like to explore a better slipper and possibly a center differential. My plan is more or less what I did hear - look up the specs for every 1/10 4wd that exists and order up a bunch to see what fits. The problem with making one off parts is once you break it, you’re in the same boat as you were before you made it. 3d printing is an interesting new avenue because you can make one off parts and just save the file or give it to others so they can essentially print up a bolt on part too. In addition to other benefits like being able to print one, test it, revise it, test it, etc

It’s still in pretty early testing, the most we’ve done with it up until today is take it for walks. Literally, walk around our property behind it like a dog. It’s done more crawler stuff than monster truck stuff so far.

Sorry for the quality, I’m driving with one hand while filming and holding a baby. My 3 year old has twin 3 month old brothers.

I got the gyro working finally. DumboRC instructions are useless. So are many Facebook groups. It turns out the orientation of the receiver doesn’t matter, but steering setting does. I use reverse steer on the radio. In order to get the gyro correct I needed to put the receiver in a different mode. I believe in giving credit to those that did the work, this guy is who I got the info from