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MT410 Rear Diff Bombing Ball Bearings

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Mirovingian

Member
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Tekno RC's
  1. MT410
Driving Style
Basher
Hey folks.

I've been having a blast with my MT410 for almost a year, but recently the rear diff ball bearings have fell apart.

I've changed em thinking that the bearings simply have gone bad, but I've changed the set twice so far, and it just keeps happening after a few full speed runs down the block (here's a pic).

Not even crazy bashing this thing, besides high speed runs off of little speed bumps.

Had the diff case changed thinking it may be warped in some way, but still no cake. Even reassembled the whole back peg from scratch to make sure it's sorted out for good but it just keeps happening, and immediately within the start of the run.

The diff pinion and ring gears are unaffected so far as well so.

Any tips or insight on this issue cause it's really getting annoying.

Thanks in advance.
 

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Wow, that's really odd. I was about to suggest that perhaps you haven't shimmed the diff. quite right, but not sure if that's the case now thinking about it. What weight oil/grease are you running in the rear? The middle?
 
Wow, that's really odd. I was about to suggest that perhaps you haven't shimmed the diff. quite right, but not sure if that's the case now thinking about it. What weight oil/grease are you running in the rear? The middle?
Had the issue first start, like hearing some creaking sounds from the back diff with stock gearing, but I took the chance during the first bearing replacement to change out the diff oils to 50k F / 100K C / 30K R to have this thing turn better.

Could that be the issue? I'd be surprised if it is. Running a 16T pinion only and on 6s, and just like a lap of full throttle runs for the bearings to give away, not a few minutes.

That can't be that much heat for those bearings to go out like that. They're even ceramic rubber sealed ones.
 
My original thinking was too light of oils in the center an rear diffs, causing it to "diff-out", but now? Not sure anymore. Sorry I'm not much help, but please let us know if you resolve the issue.
 
My original thinking was too light of oils in the center an rear diffs, causing it to "diff-out", but now? Not sure anymore. Sorry I'm not much help, but please let us know if you resolve the issue.
I have no clue man. My last resort is to change out the diff pinion gear, assuming it's warped and pressing against the bearings, though I see it spinning freely during assembly.

Would love to hear from others on the forums on the matter.

I can see a couple of threads complaining of the same issue, though not as frequent as mine.

Thanks.
 
Yeah man, sorry I wasn't more help. Could simply be just a matter of a "bad batch" of those rings? Have you swapped for a completely new rear end, spider gears, ring an all?
 
Yeah man, sorry I wasn't more help. Could simply be just a matter of a "bad batch" of those rings? Have you swapped for a completely new rear end, spider gears, ring an all?
It's all good dude. Thanks for reaching out.

I don't think so, cleaned em off and they all look great.

I recall now that i did 2 standing back flips the first time the bearings failed, and ever since then, repair after repair, the bearings blow up a few minutes in.

I got the worst luck in RC's, i swear.....Jumped from Arrma's to Tekno thinking that'll be it...I dont mind wrench time, but not once every 5 minutes for the same issue.
 
Last edited:
I think I may know the issue. The rear dog bone actually gets SUPER close to the input shaft inside the drive cup that connects to the diff. What happens is that under stress or flex, the dog bone gets pushed into the output shaft and cause it to push against the diff and blow out the bearings. I had a similar issue and deduced this to be the issue. Solution? Try a flanged bearing to put some space on the drive cup away from the diff housing so that the dog bone has a little more room when under stess or flex. You could also try some shims to space it away. Best of luck.
 
It's all good dude. Thanks for reaching out.

I don't think so, cleaned em off and they all look great.

I recall now that i did 2 standing back flips the first time the bearings failed, and ever since then, repair after repair, the bearings blow up a few minutes in.

I got the worst luck in RC's, i swear.....Jumped from Arrma's to Tekno thinking that'll be it...I dont mind wrench time, but not once every 5 minutes for the same issue.
I think I may know the issue. The rear dog bone actually gets SUPER close to the input shaft inside the drive cup that connects to the diff. What happens is that under stress or flex, the dog bone gets pushed into the output shaft and cause it to push against the diff and blow out the bearings. I had a similar issue and deduced this to be the issue. Solution? Try a flanged bearing to put some space on the drive cup away from the diff housing so that the dog bone has a little more room when under stess or flex. You could also try some shims to space it away. Best of luck.
+1

There's a thread outlining the procedure here:
https://www.teknoforums.com/threads/bulletproofing-the-gearbox.720/

Make sure that the drive cup on the pinion input shaft doesn't come loose or else the mesh between the ring/pinion will be off and you'll have issues. I've been using red loctite and knurled set screws in addition to the flanged bearing mod. I haven't had any issues using a long can motor and badlands MX38s pushing 4 HP after 200+ standing backflips, lots of crashes and lots of tumbles.

Link for knurled set screws. I use these on the tekno motor pinions, both drive cups and the four axle pins as well. They're all the same size.
https://www.boltdepot.com/Product-Details.aspx?product=25612
 
+1

There's a thread outlining the procedure here:
https://www.teknoforums.com/threads/bulletproofing-the-gearbox.720/

Make sure that the drive cup on the pinion input shaft doesn't come loose or else the mesh between the ring/pinion will be off and you'll have issues. I've been using red loctite and knurled set screws in addition to the flanged bearing mod. I haven't had any issues using a long can motor and badlands MX38s pushing 4 HP after 200+ standing backflips, lots of crashes and lots of tumbles.

Link for knurled set screws. I use these on the tekno motor pinions, both drive cups and the four axle pins as well. They're all the same size.
https://www.boltdepot.com/Product-Details.aspx?product=25612
Heck yeah! Good thread reference! I actually came to this conclusion without even thinking about searching it up so I just added some mugen shims to the input drive cup and seems to be holding up! I think on my next tear down I’ll swap out to the lipped bearings. Cheers! 🍻
 
Heck yeah! Good thread reference! I actually came to this conclusion without even thinking about searching it up so I just added some mugen shims to the input drive cup and seems to be holding up! I think on my next tear down I’ll swap out to the lipped bearings. Cheers! 🍻
Thanks peeps for all the pointers.

I've instinctively added one more shim to the diff pinion, right where it meets with the drive cup.

Not sure how much that helps but I'll try it our for now.

Will start working on the modded bearing approach as well.
 
I have the rear diff bulletproofing "kit" of parts available for sale in the classifieds section. All new parts, of course. It's a bit of a PITA to find all of the parts...
 

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