Kraton Help with Center Differential Grinding noise

[lluna2012]

Hey all,
New to the Forum, and new to RC as well. The Kraton is my first RC, and has been my only thus far. Running on a smart 6s 5000mAh 100c battery. I jumped the car about a week ago and once it landed it lacked in power and had this terrible grinding noise. I know these Kraton’s are loud, but this does not sound right to me. I cracked all three differentials open thinking I would find either chipped or broken gears. All differential gears look fine. I pulled the motor away from the gear and the motor runs fine, and sounds fine. I replaced the pinion gear just in case, but the noise still exists. I have replaced bearings and have shimmed the center differential with used shims, just to see if it would slightly help until the ones I ordered get here. The noise is still just as loud as it was. Any help would be greatly appreciated. Local hobby shop has looked into the car and could not diagnose the problem. My next step if I cannot get a solution from you guys is to send the car for warranty. Thank you for your help in advance!


Also, the link for the video is below! Thanks for looking!

 

[L3phturn]

Post it on YouTube and share the link. That’s what I do.

 

[lluna2012]

I edited the post to have a link on YouTube, can you view it on my original post?

 

[L3phturn]

Difficult to tell with it disconnected. What did the venter diff look like inside?

 

[lluna2012]

Planetary gear and satellite gears looked fine. The shims on the satellite gears are fairly worn, but used 1 additional shim for each set from the front diff to see if that would ease the noise, but it did not change the pitch whatsoever. The bearings on this differential have also been replaced with fast eddy bearings to see if that was the issue, but it was not.

 

[olds97_lss]

Sounds normal to me. With the alloy motor mount bolted to the alloy chassis, it transfers a lot of the noise to the chassis deck like a speaker. My plastic spur trucks are much quieter than my steel spur trucks in general.

 

[lluna2012]

It may be hard to tell in the video, but almost sounds as if it’s outside of the differential, if that makes sense. At this point I’m up for any suggestions!

 

[jondilly1974]

Sounds ok to me. Is the sound the only symptom?

 

[lluna2012]

As far as I know so far the sound is the only symptom. I ordered the correct shims to “bulletproof” the differentials, and will rebuild and put everything back together once they arrive and see how it runs. Just seems like there is something loose in there to me. Although, I never paid much attention to the noise prior to it breaking, other than knowing it was loud haha
Before I pulled the car apart it seemed to lack in power with the noise, but I haven’t run the car since I pulled it apart.

 

[Engineer]

Sounds Ok to me as well - how’s your pinion/spur gear mesh? Might be a little loose.

 

[jkflow]

Sounds normal. LH failed to diagnose because there is nothing wrong with it.
If it does break, fix it under warranty. If you don't like the noise only suggestion is to get used to it. I can guarantee you that the noise does not originate in any shim. Careful with all the shims. Easy to over-shim and cause actual damage.

I'd drive it all day long and not worry. You can not judge shims by 'looks', you have to measure them. Yes, you will see wear marks on metal surfaces but you can probably run 100+packs before a shim wears down, everything else will probably break prior. Still a good idea to check them.

 

[lluna2012]

Sounds Ok to me as well - how’s your pinion/spur gear mesh? Might be a little loose.

I tried to tighten the mesh up just a bit, but then it almost smells as if the metal is burning when it’s any tighter!

 

[Surchaufeur]

I think its normal but i realised the center diff gets freaking hot at least on the exb

 

[Engineer]

I tried to tighten the mesh up just a bit, but then it almost smells as if the metal is burning when it’s any tighter!

You still need to be able to hear ticking when you rock the spur gear against the pinion - if you don’t then it’s too tight.

 

[razorrc]

It could be motor bearings.

 

[lluna2012]

It could be motor bearings.

Wondered that as well so we replaced the motor at the LH, and the sound was still there when it was all back together.

 

[Yas]

The noise sounds normal to me

Is the motor mount straight? Check everything for tightness, including the diff cup screws, the motor mount chassis screws and the plastic diff mount screws too

The pinion/spur mesh seems okay albeit a little loose, although a tighter mesh may sound noiser until the teeth bed in

It may not be your centre diff at all. I would do these checks then run it as it is. If something is out of alignment a fault will make itself known eventually

 

[Camaroboy383]

Normal.. nothing wrong..

 

[jkflow]

Always hard to convince people that nothing is wrong, next they fix stuff that isn't broken. They will break something in the process or cause issues and then they believe that they found the issue... ?

 

[bicketybam]

I'd install the front and rear dogbones and test it again with the wheels off the ground. With the entire drivetrain working I bet you don't notice the "noise" from the center diff. I think you are fine.