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Metal clanking sound, motor turns, wheels barely..

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golfmonke

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Need some help diagnosing what's wrong here. The car was running fine for several weeks now (just recently bought it used) ...

Today at the end of my run I started getting a loud clanking sound ,and the wheels barely turn (when on the ground).

I took apart the center differential, didn't see any signs of any obvious damage on the teeth of the gears... there is oil in there.

I posted a video above, you can hear the metal clinking sound , although not as loud because tires aren't on the ground.

Do you think it's the motor?
 
Check the set screws on both the front and rear center out drives where the drive shafts go into the diff case... if loose, then be sure to apply some fresh gel based thread lock on those set screws :)

3241
 
Yep, I found them, they are fine, however the outdrive on the front differential appears to be busted inside somewhere, it has about an 1/8 of play in and out and I can move it side to side about a 1/4 of an inch. Would have to be the front diff, and not the rear > : |
 
you don't happen to know the minimum amount of stuff I need to remove to repair that by chance?
 
Might be a cracked gear box? If the diff is loose I would take the front end apart and inspect for hairline cracks, might be hard to spot until you start taking things apart, best way to know what to do is follow the manual but in reverse order of the assembly:
https://wwwcdn.teknorc.com/wp-content/uploads/2015/08/ET48.3instructions.pdf

Could also be a busted bearing making the diff loose, really hard to say without seeing it in person.

Good Luck!
 
I've got it apart, i'm assuming there is supposed to be oil in the front diff case, there wasn't, just a little bit of sludge, I guess old grease.....

According to the manual, looks like just grease?

Anyway, it appears one of the bearings was either never put back in, or it disintegrated, there is only 1 bearing, I guess thats why I could pull the diff pinion shaft out 1/8-1/4"
 
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My bad, i'm looking at the front gear case, not the differential case... guess just grease. Ok, guess I just need some bearings.
 
yeah there should be 1 bearing on each side of the diff case, typically there should be diff fluid filled in the sealed diff case, I would inspect the rubber seals and replace if there are any tears, you want to use grease on the rubber seals only, this will prevent the diff fluid from leaking ;)

More than likely it has been a very long time since the diff was properly serviced (normally want to rebuild the diffs every 25 battery pack cycles) and once the fluid leaked out, then you started to cook the diffs which generated excessive heat which in turn blew out the bearings... might want to inspect for any melted plastic and replace those parts as well.
 
It's the front gear case that's missing a bearing for the diff pinion. The diff I think is fine. My bad, I said diff, I was looking at the gear case.
 
3245


Might have disintegrated, did see some curled up thin pieces of metal/plastic inside gear case.
 
I see, that makes sense... try to get into the habit of pulling all your bearings out and cleaning them after every 25 battery pack cycles and then you'll never run into problems like this again... replace any crunchy bearings before they disintegrate, ha!

I use a hobby knife to carefully pry away the rubbers seals.
Then I use PFTE spray to flush my bearings.
Then I pack the bearings with fresh bearing grease.
Pop the rubber seals back on and done!

To make maintenance go faster, I like to keep a full spare set of freshly cleaned bearings when doing a rebuild, then I go back and clean/inspect/replace worn bearings to prep for the next rebuild.... also saves time so I can work the bearings separately so it's not as daunting to work on too many things in a single day.
 
I see, not sure i'm going to do it that often :)

Are the Tekno bearings good, are there better ones?
 
Yes TEKNO bearings are very good quality, but tend to be a little overpriced, there are plenty of bearing kits available from tons of brands across the net, in fact you can get decent bearings in bulk off eBay (China) too.

My personal favorite brand is AVID, just select the Rubber seals option for your needs here to make it easy to get all the bearings you need in one stop:
TEKNO Bearing Kit for ET48.3

If you don't replace your bearings before they wear out, you risk overheating/melting plastic parts and risk damaging your electronics... doing regular maintenance can save you a lot of frustration and money down the road ;)
 
View attachment 3245

Might have disintegrated, did see some curled up thin pieces of metal/plastic inside gear case.

I was once recommended to glue that bearing in the casing.

The problem is that the casing doesn’t properly hold the bearing in that spot. While the gear pinion gives the bearing enough slope to dislodge itself. That’s when the bearing gets destroyed by the torque that gets applied on it while not supported properly.

There is a bit of personal interpretation of what’s happening here, but it feels right. Will keep the group posted on further findings.

By gluing, i would suggest three glue points to keep the bearing in that spot holding to the casing and still be able to pop it out if needed.
 
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I've never had to glue a bearing under any circumstance... what can happen is if you don't properly maintain your bearings, void of grease the bearings can over heat and melt the plastic ever so slightly which can damage the gear box, it will be very subtle but can cause bad mesh with the diff case and pinion gear. If you feel the need to glue a bearing, then chances are the diff case needs to be replaced instead :)

Old grease breaks down within 20-25 battery pack cycles and needs to be flushed out... fresh grease should be applied and that will ensure your plastics will last a lifetime... I am still running the original gear boxes on my SCT410.1 which is approaching 9 years old... the key is regular bearing maintenance ;)
 
I've never had to glue a bearing under any circumstance... what can happen is if you don't properly maintain your bearings, void of grease the bearings can over heat and melt the plastic ever so slightly which can damage the gear box, it will be very subtle but can cause bad mesh with the diff case and pinion gear. If you feel the need to glue a bearing, then chances are the diff case needs to be replaced instead :)

Old grease breaks down within 20-25 battery pack cycles and needs to be flushed out... fresh grease should be applied and that will ensure your plastics will last a lifetime... I am still running the original gear boxes on my SCT410.1 which is approaching 9 years old... the key is regular bearing maintenance ;)

It could totally be a bad fix for an already worn out casing... objection accepted! ?
 

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