Kraton Kraton 4s Spurgear plastic problem

[ValentinoDisco]

Hi, today I opened up my kraton 4s drivetrain
because it made weird sounds last time I was running it. I found this:
https://drive.google.com/folderview?id=1VVvCA2YKbvgZu3jpFsOZx3fbdZAxf8rI
There are several photos of the Spurgear the pinion gear and the housing everything was covered in black soot, and I found out that it is plastic powder from the worn plastic housing.
Now my question is how can this happen and is the spurgear the reason for that. It looks like something is damaged on the backside.
Background informations : the spurgear has plenty of play in the housing and I am running a 15 T pinion, and since the last to runs it does not make wheelies any more but the slipper is tight ,not loosened

 

[Camaroboy383]

Slipper hubs were slipping alot, killed the pads, that is what the powder is... the housing started to melt by the looks of it... Time for a slipper rebuild..

 

[ValentinoDisco]

Slipper hubs were slipping alot, killed the pads, that is what the powder is... the housing started to melt by the looks of it... Time for a slipper rebuild..

Thanks

 

[ValentinoDisco]

Slipper hubs were slipping alot, killed the pads, that is what the powder is... the housing started to melt by the looks of it... Time for a slipper rebuild..

Should I replace the Slipper pads with the ones that were in there or are there better replacements

 

[VonJarga]

Should I replace the Slipper pads with the ones that were in there or are there better replacements

Hot racing makes aluminum slipper pads. I hear they can be dialed in with greater precision, but at $4 each they are a bit pricey.

 

[ValentinoDisco]

Slipper hubs were slipping alot, killed the pads, that is what the powder is... the housing started to melt by the looks of it... Time for a slipper rebuild..

I replaced my slipper pads and unfortunately, I ran it a bit too tight. It worked awesome the punch was insane but after half an hour I stripped my input gear.
Now my first question is, I want to replace the input gear and originally in there was the AR310873 Input Gear with the AR310872 Diff Case. But the original Input gear does not get produced anymore, which do I have to buy now? and the Diff Case looks relatively fine, is it okay to just replace the input gear?

 

[Roger75]

AR310873 is replaced by ARA31103. Only difference is the input shaft is a little shorter.
Depends on how much worn it is but I would replace both gears and use the old as a spare part.

​

 

[ValentinoDisco]

AR310873 is replaced by ARA31103. Only difference is the input shaft is a little shorter.
Depends on how much worn it is but I would replace both gears and use the old as a spare part.

​

do you mean ARA311031?

 

[Roger75]

do you mean ARA311031?

Yes, thats correct. Sorry, missed to write the last number.

 

[Camaroboy383]

I replaced my slipper pads and unfortunately, I ran it a bit too tight. It worked awesome the punch was insane but after half an hour I stripped my input gear.
Now my first question is, I want to replace the input gear and originally in there was the AR310873 Input Gear with the AR310872 Diff Case. But the original Input gear does not get produced anymore, which do I have to buy now? and the Diff Case looks relatively fine, is it okay to just replace the input gear?

Ring and pinion gears (crown and input) should be replaced in pairs.. especially if the one gear failed while mated to the other.. asking for a repeat failure only replacing the pinion gear...

Now let's go back a little bit to when the slipper melted down... Heat generated by the slipper has a tendency to melt and deform the diff yokes.. This is most likely the reason for the gear failure, so make sure the yokes are not deformed before replacing the ring and pinion, or again, you will be right back where you started..

A tight slipper will usually pop the shafts far before it eats pinion and ring gears.. that being said, it sure sounds like the yokes were deformed from heat and allowed the pinion to yield.. check them good, if your unsure post pictures so we can see them..

 

[ValentinoDisco]

Ring and pinion gears (crown and input) should be replaced in pairs.. especially if the one gear failed while mated to the other.. asking for a repeat failure only replacing the pinion gear...

Now let's go back a little bit to when the slipper melted down... Heat generated by the slipper has a tendency to melt and deform the diff yokes.. This is most likely the reason for the gear failure, so make sure the yokes are not deformed before replacing the ring and pinion, or again, you will be right back where you started..

A tight slipper will usually pop the shafts far before it eats pinion and ring gears.. that being said, it sure sounds like the yokes were deformed from heat and allowed the pinion to yield.. check them good, if your unsure post pictures so we can see them..

But is it normal that the slipper melts at punchlevel 5, but with the normal factory slipper setting ? And when I replace the crown can I use the old diff fluid or would that be not enough and I also have to buy diff fluid?

 

[Camaroboy383]

Yes, regardless of punch setting, if it slips enough, long enough, it melts down.. what did the yokes look like?..

You will need diff fluid, there is typically not enough in them from the factory...

 

[ValentinoDisco]

I think the Diff Yokes are looking ok but I made a drive folder with fotos of them you can check them:
https://drive.google.com/folderview?id=1agQy3K7FNzqP4raJPISDzFNMoH_ubIwR
But if the diff yokes are not deformed, what then could be the reason for breaking the input, and causing the hard abuse before.
Could the problem be the grease I used, on the outside of the diff, which is made for metal components, maybe that attacked the plastic?
And what diff fluid do I need when rebuilding the diff, for the rear and the front ?
@Camaroboy383

 

[ValentinoDisco]

Yes, regardless of punch setting, if it slips enough, long enough, it melts down.. what did the yokes look like?..

You will need diff fluid, there is typically not enough in them from the factory...

i answered your question down below @Camaroboy383

 

[Camaroboy383]

50k diff fluid works well front and rear for bashing.. if track running then lighten up some..

The yoke's look decent but still slightly heat soaked around the nose where the input bearings seat... I would replace the yoke set..

 

[GRC]

Slipper hubs were slipping alot, killed the pads, that is what the powder is... the housing started to melt by the looks of it... Time for a slipper rebuild..

Looks like this is an old post, but I disagree with the diagnosis. The slipper gear is rubbing the back of the power module, that's what creates that ring. The black dust is shredded power module housing. Shimming the slipper fixes this problem. Shim size is 15x12x0.5. They are available from a few sources. HPI sells part #101291. Shims stopped the black dust in my power module as well as other 3s owners.
https://www.arrmaforum.com/threads/blx-motor.20999/page-2#post-290367

A bent motor mount can also contribute to this problem.

 

[Camaroboy383]

Looks like this is an old post, but I disagree with the diagnosis. The slipper gear is rubbing the back of the power module, that's what creates that ring. The black dust is shredded power module housing. Shimming the slipper fixes this problem. Shim size is 15x12x0.5. They are available from a few sources. HPI sells part #101291. Shims stopped the black dust in my power module as well as other 3s owners.
https://www.arrmaforum.com/threads/blx-motor.20999/page-2#post-290367

A bent motor mount can also contribute to this problem.

Yes, this is an old post that the o.p replied to today... You disagree that the o.p burned up the clutch after he said he did?.. .. really the only way they can rub is if sand/ dirt / grit gets in there and or the bearings are smoked.. which definitely could have been.. it's common.. but we can't deny the slipper being burnt up and excessive heat and black powder leaching all over the place..

That amount of powder would warrant the housing being far worse than it is if in fact the powder came from the housing..

 

[ValentinoDisco]

☝ I think both happened my Slipper always had a lot of play in the housing but one slipperpad got also completely burned away, so the black powder was a combination of powermodule housing and a Slipperpad.

Okay now I need to plan what I have to replace:
Slipper is already rebuild✔
Shims to reduce the Slipper play in the Power Module housing
New Input Gear already bought✔
New Diff Housing
New Diff Yokes (are the metal HR Yokes a good replacement ?)
And 50 K diff fluid


Did I forgot something ?

And another question, what should I use to lubricate the Diff and the Input gear from the outside ? I used Grease for metal bearings maybe that is also a reason why the teeth of the crown and input were so heavily worn

@Camaroboy383 @GRC

 

[GRC]

He didn't say he burned up the clutch. You did. At first he said this, and he was correct.

There are several photos of the Spurgear the pinion gear and the housing everything was covered in black soot, and I found out that it is plastic powder from the worn plastic housing.

I instantly recognized the photos because that's what the inside of my power module looked like (mine wasn't quite as bad). If you check the thread I posted you'll see photos of that black dust. There is also the tell tale circle on the back of the power module. My power module and the one in the other thread were not nearly as chewed up. ValentinoDisco's power module has really deep gashes, hence more black dust. I and a few others tried out the shims and agreed they stopped the slipper from rubbing the power module and stopped the black dust.

Did I forgot something ?

Check your motor plate to see if it's bent. One thing I did not realize at the time of that other thread was that a bent motor plate was contributing to the slipper plate rubbing the power module.

 

[ValentinoDisco]

He didn't say he burned up the clutch. You did. At first he said this, and he was correct.



I instantly recognized this OP's photos because that's what the inside of my power module looked like (mine wasn't quite as bad). If you check the thread I posted you'll see photos of that black dust. There is also the tell tale circle on the back of the power module. My power module and the one in the other thread is not nearly as chewed up as the OP. The OP's power module in this thread has really deep gashes, hence more black dust. I and a few others tried out the shims and agreed they stopped the slipper from rubbing the power module and stopped the black dust.

One thing I did not realize at the time of that other thread was that a bent motor plate was contributing to the slipper plate rubbing the power module. I would advise the OP to check his motor mount to see if it's bent. I would also suggest getting some shims to prevent the slipper from rubbing the power module.

No but later I found out a burned slipperpad was also a reason for the powder. And my Motorplate was bent already one time but I straitened it. @GRC