Notorious Notorious diff issues

[Loon_tune]

So I've had diff issues with my notorious for awhile. It would make a really bad "crack" noise with under hard acceleration or breaking. I learned about shimming them and I thought I had it right. Redid all 3 diffs and even upgraded to a couple metal cups and replaced the input gears. But yesterday the cracking sound came back. Even worse than before. Open it up and I find this ;

Now it looks to me like I over shimmed the input gears but I just tried to put in enough to take out the play.

Any guidance would be most appreciated. Thank you in advance.

 

[SrC]

A certain amount of gear backlash (play) is ok and is needed. Did you open it up yet to see what is damaged? Overtightening/over shimming can crack a Sun gear and/or its cross pin. When shimming its best to shim and assemble it dry before the diff lube is filled up. Test the diff action dry to feel the gears meshing while turning it.
Why is that F/R diff alloy cup grinded down to bare alum along the whole part?
The outer ring gear looks fine to me. Any cracked teeth on the input gear?
Not that it should really matter, what weight oil did you use? What diff is that, F or R?

 

[Loon_tune]

It's the front diff filled with 60k. I haven't opened it yet, I'm going to tomorrow morning. As to the diff cup shredding, that's where I think put too many shims behind the input gear and it's rubbing. Think the cup is trashed because of it?
I put as many shims in as I did because previously it was making that horrible "crack" noise on hard acceleration or breaking and I thought it was my input gear skipping.
I've had these diffs apart a bunch of times trying to pin this down and I've never seen anything damaged but one input gear and one ring gear, both of which have been replaced.

 

[SrC]

I am experiencing the same thing on my Kraton 6S. Same symptom like you describe, a clicking/snapping sound under acceleration and when hard braking. I just keep driving it waiting for that one diff to explode. They were all recently rebuilt. Diff action is smooth for all 3 diffs. Runs fine but that noise is still a bad sign. I cant seem to duplicate the symptom on the bench. I did not shim the input gears. I never feel the need to. I would focus on the diff sat and sun gears for now. Sometimes I feel it is the exposed center diff making the noise because it is loud and pervasive enough. I only use the Arrma upgrade metal diff cup on the center. Plastic stockers for front and rear. FWIW. I cant see how over shimming the input gear would gouge the whole surface area width of that alloy diff cup unless you really overshimmed it, but then binding would be apparent from the get go. The Input gear shouldnt make full contact along its whole width.
edit: Are you also shimming the ring gear side bearing??

 

[olds97_lss]

I shimmed the input gear once, but my shims got eaten up shortly after and I ended up cooking the ring/pinion in the process. Now with arrma 2 piece diffs, I remove the cap end gasket, RTV it, then use 2-3 shims to push the ring gear into the pinion. With both gaskets, I was unable to fit any shims and the diff wouldn't even make it 2 minutes before popping.

 

[Woodentop]

Slightly out of true driveshaft? Bad bearing, more likely the bulkhead is warped, very slightly damaged? mine wasnt even noticeable but it was warped all the same, I rebuilt it with a new case and it solved the clicking ?

 

[Banging_Gears]

the pinion and ring gear both look worn down, the tips are missing. That would do it.

 

[skimeister]

I am experiencing the same thing on my Kraton 6S. Same symptom like you describe, a clicking/snapping sound under acceleration and when hard braking. I just keep driving it waiting for that one diff to explode. They were all recently rebuilt. Diff action is smooth for all 3 diffs. Runs fine but that noise is still a bad sign. I cant seem to duplicate the symptom on the bench. I did not shim the input gears. I never feel the need to. I would focus on the diff sat and sun gears for now. Sometimes I feel it is the exposed center diff making the noise because it is loud and pervasive enough. I only use the Arrma upgrade metal diff cup on the center. Plastic stockers for front and rear. FWIW. I cant see how over shimming the input gear would gouge the whole surface area width of that alloy diff cup unless you really overshimmed it, but then binding would be apparent from the get go. The Input gear shouldnt make full contact along its whole width.
edit: Are you also shimming the ring gear side bearing??

Have you solved your problem with the k6s? Mine is brand new and out of the box started making that sound under hard throttle and braking. I put one additional shim in the left side of the rear diff but no change. I’m at such a loose with it. Any help would be awesome.

 

[jondilly1974]

Have you solved your problem with the k6s? Mine is brand new and out of the box started making that sound under hard throttle and braking. I put one additional shim in the left side of the rear diff but no change. I’m at such a loose with it. Any help would be awesome.

If it already made noise the gears are likely already damaged. Pull the diff and inspect the teeth ??

 

[Nomad1981]

Hey Loon, I have the same issue. I rebuild the diff and it just happens all over again. For me the problem is with the input and ring gears. They just don't mesh right. I have aluminum gear boxes too so When opening it up it seems that the pins are broken or the input ger is missing a tooth. It could be that I am over shimming it now that I see the responses. I have 3 other well run in Arrmas and none of them have any issues. Did you ever resolve this and if so what was it. I can't figure it out for the life of me.

That input gear look warn. There's a lot of metal in that grease too from wearing the input gear down. That also is a signal something isnt fitting great. Mine was brand new and still did it after just a couple of jumps. Hope you got it fixed man. Also those HR pin holders don't last. the only thing that held up for me was the captured hinge pin holders from M2 or the JBIRC thick one. They won't bend. Just fyi.

It's the front diff filled with 60k. I haven't opened it yet, I'm going to tomorrow morning. As to the diff cup shredding, that's where I think put too many shims behind the input gear and it's rubbing. Think the cup is trashed because of it?
I put as many shims in as I did because previously it was making that horrible "crack" noise on hard acceleration or breaking and I thought it was my input gear skipping.
I've had these diffs apart a bunch of times trying to pin this down and I've never seen anything damaged but one input gear and one ring gear, both of which have been replaced. View attachment 90359

That input gear looks worn.

 

[msj226]

I feel u iv bin stumped at my table Messing with tolerances with all kinds of different gears for a few days now I’m starting to go nuts I totally understand the easiest way is to go to straight gears I’m starting to think I cannot get the tolerance in my front deaf to go smooth for the life of me my rear will go smooth but my front feels like it’s only smooth if I flip it the other way it’s horrible