Kraton Kraton EXB Diffs & Hinge Pins

[Philippe_R]

Hi there,

so i see a lot of people have problems with their EXB Diffs. Mine got wrecked simultaneously, front and rear, not because of a crash but because they wore out after maybe six full battery runs. A possible cause for this may be the friction created by the 2.6mm hole in the out drives and the 2.5mm pins. I attached a high magnification photo (IMG_1187) of one of them here. So the friction creates these two breaking points and makes my diffs go boom, tearing some gears apart as well if I'm lucky At least that's what I figured.

I came up with two "solutions" I'm testing right now, one in the front diff, one in the rear diff. But I wanted to maybe hear from you guys, what you came up with to toughen up those diffs.

So in the front diff, I used pins from my Maxx's stock hex hubs. I don't expect particularly much from this. I use 10k fluid and two shims for this one.
For the rear diff I bought German-made M-line outdrives and 2.6mm pins from Kyosho I filed (correct term?) to 2.5mm at the ends so they fit the 2.5mm "openings" (I don't know how to call it) of the gears. 10k fluid & 2 shims as well.

So that's what I'm testing at the moment but there some weird additional problem with bent rear hinge pins. The attached pics are the result of one battery run. I did a couple of jumps on my ramp and I was super careful, not to jump too high and I landed the thing perfectly all the time. No crazy stuff. Plus, it landed on very soft ground... medium high, wet grass. The things I altered for the rear suspension are RPM arms, GPM drive shafts and GPM hinge retainers... (I can't get my hands on too many m2c parts here... sadly) note that both hinge pins are bent towards the rear. So what could possibly be the cause of this? Maybe those drive shafts being a bit too long? I dunno. Or those retainers with their weird plastic balls... maybe those are a design failure. What do you think?

I use a MAX8 G2 SD - 4278SD 2250kV to power the thing. For my first 1/8 I wanted a sensored motor for some reason. It drives like a dream

So yeah, I'm thankful for any help here guys.

 

[Dan B.]

I’ve been moving away from the EXB/LSD diffs and building up new BLX diffs to replace them. Bad luck with all flavors of 29mm diffs, and I’ve had nothing but problems with the LSD diffs after super careful building and shimming. I only ever get a few packs through them before I have to rinse and repeat. They did work well on my Mojave when set up max/max/min but I’m just tired of the hassle of rebuilding them constantly. Let us know how your attention to detail and better pins work out for you, that’s some nice work.
Hinge pins just bend occasionally, definitely some soft steel there. They do take a lot of shocks though, so that might be preferable to hardened steel which could conceivably shatter or just cause the blocks and a-arms to fail, possibly damaging bulkheads as well? Hinge pins bending don’t bother me that much. Sometimes I straighten them, sometimes I replace them.
I haven’t tried the M2C stuff, but others swear by them. Where are you that makes it difficult to obtain them?
Also, welcome to the forum!

 

[parcou]

Hi there,

so i see a lot of people have problems with their EXB Diffs. Mine got wrecked simultaneously, front and rear, not because of a crash but because they wore out after maybe six full battery runs. A possible cause for this may be the friction created by the 2.6mm hole in the out drives and the 2.5mm pins. I attached a high magnification photo (IMG_1187) of one of them here. So the friction creates these two breaking points and makes my diffs go boom, tearing some gears apart as well if I'm lucky At least that's what I figured.

I came up with two "solutions" I'm testing right now, one in the front diff, one in the rear diff. But I wanted to maybe hear from you guys, what you came up with to toughen up those diffs.

So in the front diff, I used pins from my Maxx's stock hex hubs. I don't expect particularly much from this. I use 10k fluid and two shims for this one.
For the rear diff I bought German-made M-line outdrives and 2.6mm pins from Kyosho I filed (correct term?) to 2.5mm at the ends so they fit the 2.5mm "openings" (I don't know how to call it) of the gears. 10k fluid & 2 shims as well.

So that's what I'm testing at the moment but there some weird additional problem with bent rear hinge pins. The attached pics are the result of one battery run. I did a couple of jumps on my ramp and I was super careful, not to jump too high and I landed the thing perfectly all the time. No crazy stuff. Plus, it landed on very soft ground... medium high, wet grass. The things I altered for the rear suspension are RPM arms, GPM drive shafts and GPM hinge retainers... (I can't get my hands on too many m2c parts here... sadly) note that both hinge pins are bent towards the rear. So what could possibly be the cause of this? Maybe those drive shafts being a bit too long? I dunno. Or those retainers with their weird plastic balls... maybe those are a design failure. What do you think?

I use a MAX8 G2 SD - 4278SD 2250kV to power the thing. For my first 1/8 I wanted a sensored motor for some reason. It drives like a dream

So yeah, I'm thankful for any help here guys.

View attachment 285805

View attachment 285806

View attachment 285807

View attachment 285818

Hi

LSD diffs have been solid for me. It was only the rear I had an issue with. These three guys created an excellent fix for LSD to open, and I have been solid since.
https://www.arrmaforum.com/threads/kraton-exb-lsd-diff-to-open-thx-again-to-the-members.51585/


M2C hinge pins are better upgrade to those.

 

[Philippe_R]

I’ve been moving away from the EXB/LSD diffs and building up new BLX diffs to replace them. Bad luck with all flavors of 29mm diffs, and I’ve had nothing but problems with the LSD diffs after super careful building and shimming. I only ever get a few packs through them before I have to rinse and repeat. They did work well on my Mojave when set up max/max/min but I’m just tired of the hassle of rebuilding them constantly. Let us know how your attention to detail and better pins work out for you, that’s some nice work.
Hinge pins just bend occasionally, definitely some soft steel there. They do take a lot of shocks though, so that might be preferable to hardened steel which could conceivably shatter or just cause the blocks and a-arms to fail, possibly damaging bulkheads as well? Hinge pins bending don’t bother me that much. Sometimes I straighten them, sometimes I replace them.
I haven’t tried the M2C stuff, but others swear by them. Where are you that makes it difficult to obtain them?
Also, welcome to the forum!

I'll have to take a look at those other types of diffs. I'm new to Arrma, so that may take a while. I will keep you posted on how my solutions are going. I'm planning two battery runs tomorrow. After those, I'll check on the pins and I'm actually worried my center diff (stock) is still holding. Maybe that one is under less strain.

Thanks for the advice on the hinge pins. I softened the rear suspension a bit and I removed those cushions in the outdrives. They added some pressure on the drive shafts... which I doubt was any useful.

I'm from Luxembourg/Europe. I found a German online shop selling m2c which is pretty cool. But the stock is limited at least for 6s RCs. And m2c is super pricey

Hi

LSD diffs have been sold for me. It was only the rear I had an issue with. These three guys created an excellent fix for LSD to open, and I have been solid since.
https://www.arrmaforum.com/threads/kraton-exb-lsd-diff-to-open-thx-again-to-the-members.51585/


M2C hinge pins are better upgrade to those.

Thanks for that link. I'll check that out for sure

 

[Philippe_R]

Let us know how your attention to detail and better pins work out for you, that’s some nice work.

Hey Guys, I'm back with some news. It has only been a three months (lol) and I finally have enough runs with both my solutions, to be able to say something about those pins in EXB differentials.

To recapitulate, the pins in rear, front, center differentials (in that order) wore off quite fast on my Kraton EXB. Friction created two breaking points simultaneously on every single pin, with obvious consequences.

To counter this unfortunate and systematic problem, I opted for two solutions. One was filing Kyoscho 2,6mm pins to 2,5mm on both ends so they fit in diff gears while sitting in the outdrives tightly. The method did not produce any breakage. Every diff (rear and centre) held for 20 runs. When I say runs, I mean some heavy jumping, speed runs and of course bad landings. I attached some high magnification photos of those pins taken today. They show some traces of friction but no apparent breaking point. All the rest is poor craftsmanship by me (especially the first... but it worked)

However the best solution to the problem is using pins from TRX Maxx stock hex hubs (TRA8956). I used them in the front diff. After 20 Runs they did not show any trace of friction. Only thing you need to do, is cutting them to the appropriate length and you're fine. I tested them with stock and 3rd party outdrives. Both came with slightly larger pin holes (2.55mm I guess). So they could rotate and potentially create those breaking points that made the stock ones break. But they held up great. Yesterday I finally got M2C outdrives and I noticed the pin holes are slightly tighter.

At present, I use these pins in both front and rear diffs with M2C outdrives. I let you know how they hold up but I'm not that worried tbh I guess the stock pins' material quality was just bad.

In summary: Both methods work. With the Kyoscho one being a bit more maintenance but preferable with stock diff outdrives. (Edit: On M2C outdrives, the 2.6mm pins don't fit!!!). I hope this makes sense.

 

[Surchaufeur]

I have never had problem with mine. I do change the pins time to time. Better than snapping them on the RTR. I personally run LSD center and open front and rear. i waited for the fi before i ever ran mine open, so i never had a EXB diff failure.
pins have little grouves but i never snapped them or saw bulging like yours, how many shims do you use?

All of my used ones look like this I believe even some who i used for a whole year. I have like 10 or so of them i just pick and choose to replace or not if the little bump near the middle is worth enough for me.

You are one of the rare ones who managed to break the exb pins. i really want to know how you build and setup ur diffs

 

[Philippe_R]

I have never had problem with mine. I do change the pins time to time. Better than snapping them on the RTR. I personally run LSD center and open front and rear. i waited for the fi before i ever ran mine open, so i never had a EXB diff failure.
pins have little grouves but i never snapped them or saw bulging like yours, how many shims do you use?

All of my used ones look like this I believe even some who i used for a whole year. I have like 10 or so of them i just pick and choose to replace or not if the little bump near the middle is worth enough for me. View attachment 306718
You are one of the rare ones who managed to break the exb pins. i really want to know how you build and setup ur diffs

They wore off in that manner with stock config.

I now use two shims both front and rear. 30k fluid front & rear. The frontal one will be replaced with 50k soon. M2C outdrives. Standard slipper pad config on both diffs.

Since I use other than Arrma pins, I had no diff failure either. As I said, maybe it's bad metal. I even wrote to Horizon Hobby about it and they were so kind and sent me a diff. This one too wore the pins off in the same way.