Kraton Grinding noise when doing wheelies Kraton 4s V2.5

[Sorken2001]

Hello! Recently bought a kraton 4s V2.5 but i noticed grinding noise when trying to do wheelies. Has anyone had a similar problem? Figured I wanted some answers before I start wrenching. Link to video on the problem: Grinding noise Kraton 4s

Thanks!

 

[Dales396lt4]

Welcome to the forum!
That sounds like a front tire is coming unglued. Or the center Diff is unhappy.

 

[Dan B.]

Welcome to the forum, man.
Could be your front diff getting angry and diffing out with bad mesh. You should check, fill, and shim all of your diffs. They often come out of the box dry (or close to it) and not well shimmed.

 

[Boggs3010]

Don't do wheelies. Next question.

(mesh/diff)

 

[Johnny b]

I'm probably way off here but could running under that metal canopy be pronouncing that noise producing an echo?

 

[hobo]

Hello! Recently bought a kraton 4s V2.5 but i noticed grinding noise when trying to do wheelies. Has anyone had a similar problem? Figured I wanted some answers before I start wrenching. Link to video on the problem: Grinding noise Kraton 4s

Thanks!

can't hear anything

 

[RelaxC]

Sounds like maybe a bad bearing to me, maybe on a differential or the motor….?

 

[RCbuzz]

Sounds like it is just diffing out. Pull the center diff, check things out and top off/thicken up the fluid. Your front tires are ballooning which means your center diff is working hard. If the diff is metal be sure to use some blue Loctite on re-assembly.

Since the differential internals do not ride on bearings (metal sleeves), when the diff action takes place it sounds a bit funny.

 

[Dan B.]

Not to purposely disagree, but I hear a front diff with bad mesh and little or no fluid.
It’s very telling that it happens the moment the front lifts. It’s possible it’s the center diff, but my money is on the front.
If wheelies are going to be a thing, the center needs much heavier fluid.

 

[Sorken2001]

Not to purposely disagree, but I hear a front diff with bad mesh and little or no fluid.
It’s very telling that it happens the moment the front lifts. It’s possible it’s the center diff, but my money is on the front.
If wheelies are going to be a thing, the center needs much heavier fluid.

Pulled all three diffs off and noticed the front diff was a bit too tightly meshed with the smaller gear (what’s that gear called) No play between them when they are installed together and compared to the rear one that has just a bit of play (which you want i guess if it’s not too much?)

Not to purposely disagree, but I hear a front diff with bad mesh and little or no fluid.
It’s very telling that it happens the moment the front lifts. It’s possible it’s the center diff, but my money is on the front.
If wheelies are going to be a thing, the center needs much heavier fluid.

Got 50k fluid for front and 30k for the rear diffs along with 1 million for the center on the way

 

[Dan B.]

Pulled all three diffs off and noticed the front diff was a bit too tightly meshed with the smaller gear (what’s that gear called) No play between them when they are installed together and compared to the rear one that has just a bit of play (which you want i guess if it’s not too much?)


Got 50k fluid for front and 30k for the rear diffs along with 1 million for the center on the way

Those weights should work well for you. The small gear is the pinion gear (not to be confused with the motors pinion gear), the bigger one is the ring gear. They should be as close as possible while still being able to turn a full rotation without them binding somewhere. A small bit of bind or grind is ok in my book, as the diffs will break in. Some will disagree and want them perfect.
Many only ever shim the side(s) of the diff in the bulkhead to get them close, but teflon shims on the pinion for adjusting the thrust of the pinion can be awesome. They can go right against the bearing face to move the pinion slightly closer to the ring gear. If necessary, of course. Have fun with it. Shimming diffs can be a very rewarding Zen trip.

 

[Johnny b]

can't hear anything

Ok..here's what's going on: A) you need to turn up volume on video. OR B) Ya def.

 

[hobo]

Ok..here's what's going on: A) you need to turn up volume on video. OR B) Ya def.

hahaha good thinking

 

[Sorken2001]

Those weights should work well for you. The small gear is the pinion gear (not to be confused with the motors pinion gear), the bigger one is the ring gear. They should be as close as possible while still being able to turn a full rotation without them binding somewhere. A small bit of bind or grind is ok in my book, as the diffs will break in. Some will disagree and want them perfect.
Many only ever shim the side(s) of the diff in the bulkhead to get them close, but teflon shims on the pinion for adjusting the thrust of the pinion can be awesome. They can go right against the bearing face to move the pinion slightly closer to the ring gear. If necessary, of course. Have fun with it. Shimming diffs can be a very rewarding Zen trip.

I noticed the front diff ring gear was binding in one specific spot, the rest of the gear moves freely. This happens even if i remove the stock shim (No play between the ring and pinion still) The binding is not that extreme though, will this problem resolve itself during a few runs with the gear wearing down?

 

[Sorken2001]

Can’t see anything wrong with these but this is the part where the ring gear binds (a little bit)

 

[Sorken2001]

UPDATE: After adding 1 million center diff fluid and topping up front and rear diffs and also moving the shim to the opposite side on the front diff solved the grinding noise problem for me. Thank you all for the help! Really appreciate it

 

[RCbuzz]

UPDATE: After adding 1 million center diff fluid and topping up front and rear diffs and also moving the shim to the opposite side on the front diff solved the grinding noise problem for me. Thank you all for the help! Really appreciate it

Glad you got it! One of the best upgrades on the 3s/4s line is a metal diff yoke, the plastic likes to stretch under load. That and I seal my power modules to keep them clean.