Kraton Clicking and loss of acceleration

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photobasher

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Arrma RC's
  1. Granite
Symptoms:

- Clicking when I gun the throttle.
- Lack of power
- Seems to affect front and rear equally. But it could be more the rear.
- If I accelerate slowly and smoothly I can get up to high speed without this happening

Set up:
- Stock with 20t pinion and hobby wing motor fan
- 100000 oil in center diff, stock in front and rear.

I had been making smooth speed runs on pavement with no issues. Motor was staying under 113 degrees F. Ran a couple packs. Then I changed my braking to 50% power and punch level up two notches. Then this happened ?

Theories? I bet it’s a diff, but I’m not sure which one.
 
When you raise the tooth count, you might have to dial back punch. More teeth is better top end, but messes with the torque. I think the stock motor just isn't dialed in for big pinions and hard punch. Not 100% sure by a long shot, but worth looking in to
 
It's either cogging due to the large pinion or you sheared down some teeth on your ring/pinion gears. If it clicks under braking in would lean towards the busted gear teeth.
 
When you raise the tooth count, you might have to dial back punch. More teeth is better top end, but messes with the torque. I think the stock motor just isn't dialed in for big pinions and hard punch. Not 100% sure by a long shot, but worth looking in to

Thanks Notorious. That’s my theory too. I’m new to the Kraton, and to creating a speed setup, so I knew I’d break something sooner rather than later!

It's either cogging due to the large pinion or you sheared down some teeth on your ring/pinion gears. If it clicks under braking in would lean towards the busted gear teeth.

From what I can see the pinion and and ring gear, but I’ll disassemble for a closer look. Also, what is “cogging”?

Do you guys have any strategies for narrowing down which diff is busted without taking each apart?
 
From what I can see the pinion and and ring gear, but I’ll disassemble for a closer look. Also, what is “cogging”?

It's a stuttering when accelerating from a dead stop. See my video below.

 
Yeah, that’s pretty similar to what I’ve got going on.

It can be hard to tell between cogging and stripped gears. It's not hard to remove the front and rear diffs. Take them out and check the teeth on the ring gears. While they are out you can look at the pinion gears. Use a flashlight so you can really inspect the teeth of the gears. If they are chipped, broken or worn down they will skip under hard acceleration and/or braking. You can also check the mesh between the ring and pinion gears. Most people have to add another shim (or several) to get a nice solid mesh. Lastly, make sure the diff housing cover is on tight and that the 4 screws that hold it on aren't stripped out. That would cause the mesh to become loose as well.
 
It can be hard to tell between cogging and stripped gears. It's not hard to remove the front and rear diffs. Take them out and check the teeth on the ring gears. While they are out you can look at the pinion gears. Use a flashlight so you can really inspect the teeth of the gears. If they are chipped, broken or worn down they will skip under hard acceleration and/or braking. You can also check the mesh between the ring and pinion gears. Most people have to add another shim (or several) to get a nice solid mesh. Lastly, make sure the diff housing cover is on tight and that the 4 screws that hold it on aren't stripped out. That would cause the mesh to become loose as well.

Great advice. So in the case of cogging, what is actually going on mechanically?
 
Great advice. So in the case of cogging, what is actually going on mechanically?

It has to do with the motor and its communication with the ESC. I can't explain it very well but others here can. If you google sensored vs. unsensored motors it will explain it to a degree.
 
You need to reduce the pinion or the punch. It's not uncommon for the motor to react the way yours has. Uncensored motors are very finicky in that they require a certain amount of voltage to turn at a certain rate. By changing the pinion and the punch, you are asking a basic motor to change the way it was intended to function. Like @bicketybam said, a sensored motor would likely allow for fine tuning of the motors parameters. Your stock unsensored motor will not. You need to decide if you want higher top speed and forfeit low end torque, or go back to a stock pinion, and accept that a higher punch rating will inevitably limit that top speed.
 
You need to reduce the pinion or the punch. It's not uncommon for the motor to react the way yours has. Uncensored motors are very finicky in that they require a certain amount of voltage to turn at a certain rate. By changing the pinion and the punch, you are asking a basic motor to change the way it was intended to function. Like @bicketybam said, a sensored motor would likely allow for fine tuning of the motors parameters. Your stock unsensored motor will not. You need to decide if you want higher top speed and forfeit low end torque, or go back to a stock pinion, and accept that a higher punch rating will inevitably limit that top speed.

Thank you both! I learn something new everyday! I’ll try adjusting the punch settings. It was plenty punchy with the stock settings before. I just thought I’d experiment.

I’ll let you know if that fixes it. I’m glad to hear I may not have to rebuild a differential!
 
I’ll let you know if that fixes it. I’m glad to hear I may not have to rebuild a differential!


you will eventually have to tho.. Sooner then later no less as diff fluid don't last forever, it leaks.. ect ect.. at least once a month depending on how often you bash your gonna wanna rebuild them, replace gaskets ect ect.

Its routine maintence with these things much like real cars and oil changes.
 
When I cooked my first diff in my outcast, it was a loud POP POP POP under heavy acceleration and braking. Not sure what it sounds like when it's the gears inside a diff though.

When I tore it down, the tips of about 5 teeth on the ring gear were dulled. The top 2 diff case cap screws had stripped out the plastic and weren't holding the diff in place tightly. The t-bone wheelie bar I installed caused me to do that as my cinder blocks for hands don't know what "tighten gingerly" means.

I take that back... it was my front diff.
2018-0820-OutcastFrontRingDamage.JPG


I did mess up my rear diff later on though because of the tbone install.
 
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