New Traxxas truggy????

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X-Maxx same wriggle on the right side when I move the drive-cup back and forth. While tightly shimmed sideways. That bearing is certainly not tight in the cover and bulkhead on the right side.

Could you guys go wriggle back and forth on the right rear drive-cup on XRT / X-Maxx? Don't need to open / unscrew anything to check.
 
Update:

Think I found the cause. Installed the cover without the diff. Tried to wriggle it sideways with pliers. No chance. Nothing moving. So there is no reason the get the aluminium upgrade for that reason. Then installed the broken differential and put the rear cover on. No moving sideways with shims. But moving back and forward certainly. More on the side where with no shims. As much play as a badly shimmed differential. Broken gears basically guaranteed. Never even thought about checking play in the forward/backward direction.

So either the top rear bulkhead or the cover is not fitting right resulting in play in the forward / backward direction while the sideways play is shimmed away. I assume the cover is not manufactured according to specifications / faulty production. Will get a new plastic cover or file down the old one to check. And obviously check if the same thing happens with the new one and file that one down in necessary.

Certainly do have a collection of some broken ones. This is not even all of them. Hope I solved that problem...


View attachment 349477
Any other suggestions?
by forward/backward you mean you didn't shim the input gear? you shimmed the ring gear instead? if so that is definitely your problem imo. The input gear shimming is way more important. Sorry if I'm misunderstanding. :eek:
 
Isn’t the rule of thumb with the Xmaxx to change the bulkhead if you wreck a differential?
 
by forward/backward you mean you didn't shim the input gear? you shimmed the ring gear instead? if so that is definitely your problem imo. The input gear shimming is way more important. Sorry if I'm misunderstanding. :eek:
Thanks for the reminder! Did not shim that one. 🫣

I'll have to check. Waiting for the new covers. There is just too much play on the right side.
 
Thanks for the reminder! Did not shim that one. 🫣

I'll have to check. Waiting for the new covers. There is just too much play on the right side.
haha I actually did the same exact thing. I've never had to shim input gears on arrma rigs before so I kind of just ignored it and shimmed how I would normally shim an arrma rig and my ring gear broke again lol. I don't think I went through as many ring gears as you but I definitely felt the frustration on my blue xrt. I even wasted money on the hot racing diffs and I managed to break those too until I shimmed that input gear :ROFLMAO: :ROFLMAO:
 
haha I actually did the same exact thing. I've never had to shim input gears on arrma rigs before so I kind of just ignored it and shimmed how I would normally shim an arrma rig and my ring gear broke again lol. I don't think I went through as many ring gears as you but I definitely felt the frustration on my blue xrt. I even wasted money on the hot racing diffs and I managed to break those too until I shimmed that input gear :ROFLMAO: :ROFLMAO:
Good you here on the forum!

I remember I checked if I could shim there and saw it would only put the pressure on the inner ring of the bearing and thought it would not a good solution. Then just dismissed it and forgot about it long ago. Years back when I got the X-Maxx. Totally brushed that possibility away. Could have saved me a lot of wrenching. Pretty sure it's not the cover. Checking now the input gear is also only on the inner ring of the bearing - should have seen that.

Thanks!

Found this video:

 
Front stub axle XMaxx, time for replacement. XMaxx was suddenly braking at low speed in front. Pin was slipping. Interesting how the pin wore down.

20240316_083935.jpg
 
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Good you here on the forum!

I remember I checked if I could shim there and saw it would only put the pressure on the inner ring of the bearing and thought it would not a good solution. Then just dismissed it and forgot about it long ago. Years back when I got the X-Maxx. Totally brushed that possibility away. Could have saved me a lot of wrenching. Pretty sure it's not the cover. Checking now the input gear is also only on the inner ring of the bearing - should have seen that.

Thanks!

Found this video:

Totally missed this reply but I used this video


I bought the same shims he used in the video too.
 
Front stub axle XMaxx, time for replacement. XMaxx was suddenly braking at low speed in front. Pin was slipping. Interesting how the pin wore down.

View attachment 354863
Looks like the inner hub bearing seized at some point? The axle looks pretty beat up from spinning against the inner bearing race. So the pin is too loose in the stub or the pin itself is too short? I wish I could give you mine, hardly any use on them, I put +10mm with steel stubs on mine after a month of ownership so I could run Arrma 8s tires/wheels. The steel axles are heavy as heck compared to the aluminum parts though. Not crazy about that part of the steel pieces.
 
Looks like the inner hub bearing seized at some point? The axle looks pretty beat up from spinning against the inner bearing race. So the pin is too loose in the stub or the pin itself is too short?

Yes the inner bearing seized a few years back. Basically I have been hammering the XMaxx. Insane what it can take. Just used it less since I have the XRT. Wanted to change the stub axle like two years ago - forgot about it - but now the pin was too loose and actually slipped inside. I first thought the front diff had something broken but that looked fine and only then found the worn down stub axles. Drilling another 2 holes 90 deg further in the stub axle should do fine. Thought of that too late, ordered now ones.

I'm amazed how the pin wore down.


The XRT rear diff is giving me some trouble. Shimmed it tightly sideways and behind the input gear. Ring gear destroyed during first lipo. Did the same again, added two more shims behind the ring gear. Then again. Ring gear teeth broken with first lipo. Have not opened it yet but seems to be the ring gear.

@Moirae - So that idea from the video to remove the spur to see how much play is really there is the next step. And actually opening down to the lower bulkhead and see if there is something more I'm missing. The XMaxx rear diff on the other hand is perfect. Perhaps even one screw thread in the bulkhead damaged and the cover perhaps moving when under power? But there is no gap to be seen. Will have to dig into this.
 
Yes the inner bearing seized a few years back. Basically I have been hammering the XMaxx. Insane what it can take. Just used it less since I have the XRT. Wanted to change the stub axle like two years ago - forgot about it - but now the pin was too loose and actually slipped inside. I first thought the front diff had something broken but that looked fine and only then found the worn down stub axles. Drilling another 2 holes 90 deg further in the stub axle should do fine. Thought of that too late, ordered now ones.

I'm amazed how the pin wore down.


The XRT rear diff is giving me some trouble. Shimmed it tightly sideways and behind the input gear. Ring gear destroyed during first lipo. Did the same again, added two more shims behind the ring gear. Then again. Ring gear teeth broken with first lipo. Have not opened it yet but seems to be the ring gear.

@Moirae - So that idea from the video to remove the spur to see how much play is really there is the next step. And actually opening down to the lower bulkhead and see if there is something more I'm missing. The XMaxx rear diff on the other hand is perfect. Perhaps even one screw thread in the bulkhead damaged and the cover perhaps moving when under power? But there is no gap to be seen. Will have to dig into this.
That's a great idea to drill a new hole at 90 degress, like new again!👍 I concur, my Xmaxx has impressed me over and over for 2+ years now!👌 What a truck!! I literally have not even touched a diff on it, bearings, but, no shims, fluid changes..nothing. Can't complain about that.
I'm no expert with diff shimming, seems every time I mess with one, it grenades shortly thereafter, LOL. As such, I'll buy a complete new assembly and drop n go whenever possible. I feel they have to have a bit of free play, at least at the pinion. Needs to be able to float forward and backward like a millimeter or 2. Many times I've opened diffs to find evidence of the pinion digging into the diff cup, I suspect the pinion was too tightly shimmed, IDK.
Good luck with the XRT brother. When in doubt..swap it out. Bulkhead, diff cover and complete diff is what I do when I can't get one to stay together.🤷‍♂️🍻
 
Yes the inner bearing seized a few years back. Basically I have been hammering the XMaxx. Insane what it can take. Just used it less since I have the XRT. Wanted to change the stub axle like two years ago - forgot about it - but now the pin was too loose and actually slipped inside. I first thought the front diff had something broken but that looked fine and only then found the worn down stub axles. Drilling another 2 holes 90 deg further in the stub axle should do fine. Thought of that too late, ordered now ones.

I'm amazed how the pin wore down.


The XRT rear diff is giving me some trouble. Shimmed it tightly sideways and behind the input gear. Ring gear destroyed during first lipo. Did the same again, added two more shims behind the ring gear. Then again. Ring gear teeth broken with first lipo. Have not opened it yet but seems to be the ring gear.

@Moirae - So that idea from the video to remove the spur to see how much play is really there is the next step. And actually opening down to the lower bulkhead and see if there is something more I'm missing. The XMaxx rear diff on the other hand is perfect. Perhaps even one screw thread in the bulkhead damaged and the cover perhaps moving when under power? But there is no gap to be seen. Will have to dig into this.
That's bonkers. Are you sure the bulkhead isn't cracked or something? there has to be some underlying reason why this is happening. I send my 12s xrt with stock diffs that I haven't even shimmed yet and I still haven't had a single problem with that one. I wonder if you need to add even more shims?! I'm so curious :eek:
 
Yes the inner bearing seized a few years back. Basically I have been hammering the XMaxx. Insane what it can take. Just used it less since I have the XRT. Wanted to change the stub axle like two years ago - forgot about it - but now the pin was too loose and actually slipped inside. I first thought the front diff had something broken but that looked fine and only then found the worn down stub axles. Drilling another 2 holes 90 deg further in the stub axle should do fine. Thought of that too late, ordered now ones.

I'm amazed how the pin wore down.


The XRT rear diff is giving me some trouble. Shimmed it tightly sideways and behind the input gear. Ring gear destroyed during first lipo. Did the same again, added two more shims behind the ring gear. Then again. Ring gear teeth broken with first lipo. Have not opened it yet but seems to be the ring gear.

@Moirae - So that idea from the video to remove the spur to see how much play is really there is the next step. And actually opening down to the lower bulkhead and see if there is something more I'm missing. The XMaxx rear diff on the other hand is perfect. Perhaps even one screw thread in the bulkhead damaged and the cover perhaps moving when under power? But there is no gap to be seen. Will have to dig into this.

I’m almost 99% positive when you wreck a ring gear on the Xmaxx and XRT, Traxxas advises installing a whole new bulkhead.
 
I’m almost 99% positive when you wreck a ring gear on the Xmaxx and XRT, Traxxas advises installing a whole new bulkhead.
I do have a new bulkhead installed. I tightened the screws for the servo too much and damaged the mount for the servo so I installed a new bulkhead. Might be the problem... :unsure:

That's bonkers. Are you sure the bulkhead isn't cracked or something? there has to be some underlying reason why this is happening. I send my 12s xrt with stock diffs that I haven't even shimmed yet and I still haven't had a single problem with that one. I wonder if you need to add even more shims?! I'm so curious :eek:
I'll have to open and check. I used to send the XRT on long and high jumps without a problem. There is no more space for shims. So tight.


Cause and effect. Pretty simple. There is an underlying reason for it all. All logical. I just have to get it. :ROFLMAO:😋:unsure:
 
I do have a new bulkhead installed. I tightened the screws for the servo too much and damaged the mount for the servo so I installed a new bulkhead. Might be the problem... :unsure:


I'll have to open and check. I used to send the XRT on long and high jumps without a problem. There is no more space for shims. So tight.


Cause and effect. Pretty simple. There is an underlying reason for it all. All logical. I just have to get it. :ROFLMAO:😋:unsure:
I will say that when I was busting rear ring gears I went through about 4 of them back to back and I never changed the bulkhead when I finally fixed it. Matt could be right but thankfully I didn't have to do that.
 
Hi everyone I got those same shims a long time cause I was planning to go over my diffs and found no need to use on my xrt. Then I started to add vitavon upper and lower bulkheads with gpm diff housings and hardened cheap Chinese gears from alli and never had to add any shims. I haven't had any gears breaks yet and have had these parts on for about 8 months and I do grease the gears often. My opinion is I don't think we need shims. Good luck with yours and maybe the bulkheads are worn and need to be replaced,their cheap and would replace them if I was breaking gears that often.
 
Found two issues. Not sure if they are related.

So basically those 3 teeth were still matching with the output gear as not the whole length is broken. But kind of makes sense to change that input gear. :ROFLMAO: Pretty sure that happened when I was trying to jump over a road and was chassis slapping on the pavement. Broke the center skid plate.

20240317_214728.jpg


Next issue is that the input gear was pushed too much forward on to the flange of the rear diff ring gear. I thought that might be the problem but was just guessing. So the ring gear was not matching nicely with the input gear even though it felt absolutely tight.

20240317_214737a.jpg


Here another picture without the shims behind the input gear. So basically that means shimming the rear differential sideways is still the best way. Shimming behind the input gear with perhaps max 0,5mm. But even that could be too tight if tolerances of parts are adding up according to Murphys law.

20240317_214759.jpg


Was interests me most if a broken output gear on the cush drive could result in a rear diff ring gear beeing damaged. I think not??


Not sure why the rear diff ring gear was damaged before as I had shimmed tightly sideways. I think the right solution would have been a bit of shimming behind the input gear and then reduce the play with shims on the side. Actually hoped to find some crack in the rear bulkhead but nothing.

Input welcome.
 
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The way that pinion on rear diff is wearing looks like to much pressure on ring gear with the shim and also the shim on the back of pinion looks like it's putting to much pressure on pinion and possibly wearing pinion gear.
 
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