Kraton Does this Motor sound normal?

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mark_paul

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Arrma RC's
  1. Kraton 4s
Hi Guys.

I posted last year with an issue I had after my Kraton 6s had a large frontal impact. After the winter, and a rebuild of a Rustler I'm back to troubleshooting the Kraton. I'm a relative noob when it comes to all this, hence the Rustler rebuild to help knowledge-wise.

Old Thread https://www.arrmaforum.com/threads/limited-speed-and-strange-noise.13623/

From the previous thread, it seemed that it may be the centre diff, but that looks immaculate so I decided to test the motor while not connected to anything.

To me, it seems to not be performing as id expect, but I've never ran this motor on its own so couldn't tell.

What do you guys think, does this motor sound ok?

If that appears ok, ill move onto the front diff as that's what took the biggest impact.

Any help would be great.

 
Ok! So all three diffs have been checked and there are no obvious signs of damage (no missing teeth, nothing snapped etc). Saying that though the front diff is definitely making a strange sound when it is in place and meshed.

Can any experts cast their ear over this video and see what they think.

 
Motor sounds perfectly normal

The front diff also sounds okay, maybe a tiny bit tight on the pinion/ring gear mesh? Check if the input gear has any play or any damage. This will be way easier with the whole front bulkhead off

Whilst the bulkhead is off I would check if there's any cracks or damage in the diff housing

Lastly you'll notice that you may have a shim at the bearing on the ring gear side of the diff. You can try putting that on the other bearing facing outwards if the mesh still feels a little notchy. And don't overtighten the diff housing cover when putting it back on ?
 
Cheers Guys. Think my issue is im not 100% sure how the diff should feel when removed.

The Centre diff feels tight, and i can't feel any teeth meshing together, completely smooth.
The front diff feels smooth, but i can feel the teeth meshing together.

Is that how they should feel?
 
Last edited:
Cheers Guys. Think my issue is im not 100% sure how the diff should feel when removed.

The Centre diff feels tight, and i can't feel any teeth meshing together, completely smooth.
The front diff feels smooth, but i can feel the teeth meshing together.

Is that how they should feel?
The spur at the centre diff against the motor pinion SHOULD NOT feel tight. There should be a slight bit of play between the pinion and spur. When setting this mesh, you should be able to rock the spur a tiny amount back and forth with your finger and hear a little tap between the gears

Is the motor straight when fitting to the mount or at a slight angle? Considering you had a stack, you may have bent the motor mount. If it's straight, try setting the motor around 1mm further away from the spur

The front and rear diffs should not have the same play, as long as you don't have any binding noises or notching (from the video, the front sounded slightly notchy when being rotated)
 
Hi Guys.

I posted last year with an issue I had after my Kraton 6s had a large frontal impact. After the winter, and a rebuild of a Rustler I'm back to troubleshooting the Kraton. I'm a relative noob when it comes to all this, hence the Rustler rebuild to help knowledge-wise.

Old Thread https://www.arrmaforum.com/threads/limited-speed-and-strange-noise.13623/

From the previous thread, it seemed that it may be the centre diff, but that looks immaculate so I decided to test the motor while not connected to anything.

To me, it seems to not be performing as id expect, but I've never ran this motor on its own so couldn't tell.

What do you guys think, does this motor sound ok?

If that appears ok, ill move onto the front diff as that's what took the biggest impact.

Any help would be great.

Don’t run your motor without a load like that. You can easily exceed the maximum RPMs and cook it. One small pull or two is probably ok but any full pulls could be a disaster.
 
Thought id upload a video of the car at full throttle but on the bench. This is 4s with Batteries.

It does just sound very noisy, I know Arrma can be, but it sounds very mechanically unsympathetic.

Don’t run your motor without a load like that. You can easily exceed the maximum RPMs and cook it. One small pull or two is probably ok but any full pulls could be a disaster.

Thanks, good to know, could have been an expensive mistake!
 
The spur at the centre diff against the motor pinion SHOULD NOT feel tight. There should be a slight bit of play between the pinion and spur. When setting this mesh, you should be able to rock the spur a tiny amount back and forth with your finger and hear a little tap between the gears

Is the motor straight when fitting to the mount or at a slight angle? Considering you had a stack, you may have bent the motor mount. If it's straight, try setting the motor around 1mm further away from the spur

The front and rear diffs should not have the same play, as long as you don't have any binding noises or notching (from the video, the front sounded slightly notchy when being rotated)

Sorry, that was a poor description by me. The centre diff does have a play when against the motor pinion and mounted. The stiffness was referencing when the diff was out and I was turning it by hand. Felt stiff and completely smooth, no grinding or meshing issues.
 
If you back the motor pinion off the spur gear and roll the truck by hand, does it move smoothly? Will it roll easily on a smooth surface? Will it stop quickly by itself? Something seems sticky in that video, like you might have a seized bearing somewhere. Hard to tell thru the video, but when you let off throttle a few times, it seemed like you had a drag brake effect.
 
If you back the motor pinion off the spur gear and roll the truck by hand, does it move smoothly? Will it roll easily on a smooth surface? Will it stop quickly by itself? Something seems sticky in that video, like you might have a seized bearing somewhere. Hard to tell thru the video, but when you let off throttle a few times, it seemed like you had a drag brake effect.

Seems to roll pretty freely, a good shove and it will coast a good few meters. I wouldn't say it feels overly sticky.

The front diff is definitely noisy, sounds a little gritty. Wouldnt this limit initial punch though and not top speed?
 
Seems to roll pretty freely, a good shove and it will coast a good few meters. I wouldn't say it feels overly sticky.

The front diff is definitely noisy, sounds a little gritty. Wouldnt this limit initial punch though and not top speed?
Of course it could. Have you spun the front wheels opposite directions by hand? If it’s not smooth, I would inspect that diff or replace it.
 
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