Kraton Grinding noise *Please help*

[Jondylondy]

Been chasing this annoying grinding noise for a few weeks now. I checked all of the diffs, gear mesh and replaced all the bearings. I'm fairly new to this so I ran out of things to check. I feel that it doesn't have the punch (no wheelies) anymore either. Check it out and any help is appreciated. First time poster as well

 

[Slevin]

Sounds like one of the gears in either diff has broken teeth. When you take the diffs apart you really have to look at the teeth closely. Your truck will sound like that even if one tooth is broken and I don’t mean completely missing. It could look dull and make that sound but it should be noticeable.

 

[jkflow]

My guess, your input gear is shot. Either front or back or both.
https://www.arrma-rc.com/part/AR310498

 

[Jondylondy]

Thank you for the quick responses. I'll take them apart again and do a thorough check. I did touch every single gear when I was replacing the bearings, but obviously the problem still exist. So I'll check again thank you

 

[Clubin]

It’ll be hard to see. You’ll need to clean em all up real good and look closely.

 

[Snoprosledneck88]

I would say Input gear. You will have to change the ring gear on the diff also if the input gear is wore out. Mine went out and one or the other took out the other one.

 

[Jondylondy]

I would say Input gear. You will have to change the ring gear on the diff also if the input gear is wore out. Mine went out and one or the other took out the other one.

Noob question.... what is the ring gear?

 

[jondilly1974]

Noob question.... what is the ring gear?

The main gear of the diff that the input gear meshes with.

 

[3d-rc.myshopify.com]

Easy check takes 2 seconds. Lift front and and push down on rear. Hit the throttle. Then lift rear and push front down and hit throttle. Bingo , which ever is down when you hear it that's the side. Not often the center goes.

 

[Jondylondy]

Easy check takes 2 seconds. Lift front and and push down on rear. Hit the throttle. Then lift rear and push front down and hit throttle. Bingo , which ever is down when you hear it that's the side. Not often the center goes.

I just did that and you can clearly hear the difference. It's the rear! THANK YOU

 

[3d-rc.myshopify.com]

I just did that and you can clearly hear the difference. It's the rear! THANK YOU

Not a problem. ? I bet you could feel it to lol... ok hit a parts breaker and buy the whole diff housing with diff. So much easier that way.
Then buy these shims and add 1 to the crown side so that there is 2 of them. Do it to front and rear diff.

 

[Jondylondy]

Not a problem. ? I bet you could feel it to lol... ok hit a parts breaker and buy the whole diff housing with diff. So much easier that way.
Then buy these shims and add 1 to the crown side so that there is 2 of them. Do it to front and rear diff.

I got some shims for both inside and out for the diffs... so I removed the rear diff and found this (haven't opened to check inside yet). A few teeth look really dull

 

[jkflow]

Yes, your main gear is stripped. By default, your input gear must be shot as well. Typical sign of wear and tear with too much play.
Look into adding a shim to the input gear and maybe 2 on the side of the diff with the gear.
By all means, your input gear and main are trash. Do not re-use.

I suggest getting one full new diff from Jennys and order a spare main and input gear. That way you will always have a drop in replacement.
Might as well order 2 as price is almost equal between parts and Jennys. Any 6S diff will do.

Input gear shims
- 8mm Input gear shims Part# ptk-h-5909 + kyo96773:
https://www.amazon.com/gp/product/B00VR5JCS8/
https://www.amazon.com/gp/product/B003XRIO28/

 

[Wmorgan]

I had same issue with my Kraton when i got back into RC a year ago. It was the rear input gear. See pic for new vs used.

The initial removal of the input gear can be a PITA due to all of the red loctite they put on the grub screw for the input cup. You'll need to apply some heat to melt the loctite.

 

[jkflow]

There is a reason for the red loctite on the input gear. If you use blue, make sure it cures before using.
Also, take out the cup and see if that screw goes all the way onto the shaft. The red loctite has the tendency to block the screw from going down all the way. You can burn away with heat or re-thread.
You must let the loctite cure (12h?) upon re-assembly.

That should get you back up and running.

 

[Jondylondy]

Thank you all for the great info.. I'm still fairly new to the hobby so all the tips and tricks are appreciated. I ordered shims, input and main gears. I have a set to build so I can just drop and go when needed. I only had the truck for a couple months but bashed pretty hard. I want to upgrade motor and esc next. I've seen a couple threads here but.... I haven't seen anyone talk about the max 8 4274 motor combo... is this a good motor?

 

[jkflow]

Max 8 is close to stock i.e. you will not see much of a change. For an 'upgrade' you want max6 but other changes are needed. Lower kv needs a larger pinion. max6 and 4985 with 20T pinion is a nice upgrade for bashing. It will backflip on you if you are throttle heavy.

 

[3d-rc.myshopify.com]

Max 8 is close to stock i.e. you will not see much of a change. For an 'upgarde' you want max6 but other changes are needed. Lower kv needs a larger pinion. max6 and 4985 with 20T pinion is a nice upgrade for bashing. It will backflip on you if you are throttle heavy.

I use a 23 t pinion and it is sickening fast

 

[GottaGetEm]

Not a problem. ? I bet you could feel it to lol... ok hit a parts breaker and buy the whole diff housing with diff. So much easier that way.
Then buy these shims and add 1 to the crown side so that there is 2 of them. Do it to front and rear diff.

Was wondering what shims I needed. Ordered two. Thanks @Lovestricken

 

[Jondylondy]

I use a 23 t pinion and it is sickening fast

What pinion brand do you recommend?