Kraton Kraton EXB V2 Diffs - Remaining Issues?

[nyev]

Hi All, first post here. I've just picked up my Kraton EXB and after researching the boards here, inspected the diffs to ensure I have a "V2" Kraton with the initial diff issues fixed. Turns out I do have the V2 version, with all limited slip diffs with the rear diff in the "minimal effect/1 face" configuration.

I've read threads indicating that all you need to do with the updated/revised Kraton EXB is check the fluids "and send it", and possibly replace the slip plates in the rear with specific shims for an open rear diff - a solution apparently identified on these boards and adopted by Arrma as I understand it.

However, I purchased a couple of spare assembled limited slip diffs (ARA310990), which are identical to the diffs in my EXB, and noticed that one of the diffs I purchased is much "notchier" than the other one that I purchased. It's also notchier than the ones I pulled off my Kraton EXB. By "notchy", I don't mean harder to turn; just that you can distinctly feel every tooth as you turn the out-drives, whereas on all the other diffs you can't really feel the teeth as you spin them. I disassembled and reassembled the notchy diff, and it remains notchy. Also tried adding fluid - and it's still notchy.

My first question is, is the notchy diff in need of shimming adjustments? If so, how - in the updated limited slip diff, if I went to thinner shims at the ends of the diff cup, in theory reducing the notchiness, then there would be too much play in the out-drive and pin - right?

My second question is, there is the smallest bit of play when I wiggle the out-drives - meaning the tiniest bit of slop underneath the pin where the two shims and o-ring are. This is just barely detectable, but equally present in all diffs. Is this okay?

Any advice is welcome! Hopefully I've posted this in the right area - let me know if not.

 

[#ARRMArcfanboy4life]

my diffs sound notchy too I am looking for a fix (talion 6s v3)

 

[Engineer]

If it feels notchy but isn’t any harder to turn then just leave it and run it.

 

[nyev]

Thanks, I went back to check, and I need to restate that the notchy diff is a BIT harder to turn than the other diffs. But, not by a big difference, and it certainly isn't sticking at all. The others are just smooth and glide, whereas the notchy one has definitive "clunks" between teeth. Guessing this is not an issue? And even if it was an issue, would there be any way to tune the shims? As I mentioned I can't see how there would be any workable way to adjust shimming on the new Kraton EXB diffs, since switching to thinner ones would free up the notchiness but add slop to the area under the pins and would introduce play to the drive cups.

 

[nomis38]

This is how both lsd diffs ive gotten are. I just run them the way they are and so far so good. But I thought it was messed up and even contacted the seller. A few days later when the next one showed up from a different seller, it was the same way. Im still a bit baffled by it as well. But the diffs are going strong.

 

[nyev]

Good to know; thanks! Now I'm wondering if the diffs I have that AREN'T notchy have an issue, lol.....

With this input, probably best for me to just finish the build and see how it goes Just seems sketchy to me that the diffs are so different to spin by hand - hard to think that it wouldn't impact performance one way or another, and not the most confidence-instilling when there are such differences between diffs, with no clear way to adjust internal shimming (at least that's my understanding with the updated EXB lsd diffs).

 

[nomis38]

My two exb open diffs are free as a bird. Its gotta just be the plates in the lsd

 

[nyev]

For anyone who is interested, last night I was trying to narrow down which component is causing the notchiness by swapping out the internals from my smoother lsd diffs, one by one. But every time I rebuilt it, it was still notchy. Then, I finally put all of the "notchy" internals into the diff cup that originally had the smooth motion, and once built up it was smooth. Therefore, it seems that the problem was due to a variance in the depth of the diff cup itself. I don't have digital calipers to measure the diff cup depth precisely, but it's the only explanation following my experimentation.

I don't like moving on from these types of issues without fully understanding, so now I know! I won't be using that particular diff cup in my build.

 

[jackka]

For anyone who is interested, last night I was trying to narrow down which component is causing the notchiness by swapping out the internals from my smoother lsd diffs, one by one. But every time I rebuilt it, it was still notchy. Then, I finally put all of the "notchy" internals into the diff cup that originally had the smooth motion, and once built up it was smooth. Therefore, it seems that the problem was due to a variance in the depth of the diff cup itself. I don't have digital calipers to measure the diff cup depth precisely, but it's the only explanation following my experimentation.

I don't like moving on from these types of issues without fully understanding, so now I know! I won't be using that particular diff cup in my build.

That makes sense. I believe the notchiness would come from the gears being tightly fit together, and the smoother ones likely being fit tightly enough to not slip, but not tight enough to cause notchiness. I wasn't sure if there were any way to control how close together the gears are meshing inside the diff, but it seems the allowed manufacturing tolerances in the diff cups themselves might be creating the diff gear mesh tightness ranging between "just right" and "slightly tight but functionally fine". If this is the case, they may wear in and become smooth with use over time. Or you might be able to control the tightness by attempting to slightly sand down the exact surface where the tolerance variance causing the tightness is occurring. Seeing as how the notchiness may not be causing any harm in operating the vehicle other than perhaps some negligible addition or subtraction to the slip level of the diff, it may be best to leave it as is. If the slip level difference was big enough it could maybe be countered by using thinner diff fluids. Maybe you can try to gauge how much harder of a rotation it is actually causing by experimenting with different diff fluids on the smooth diffs and finding which ones are about as hard to turn. With everyone having their own preference in diff fluid weight and it being somewhat of a subjective preference, the whole notchiness may be more of a psychological effect than one affecting actual use.
Also, apparently the diff plates have a certain direction that they are supposed to face when they are assembled as they have a rounded side and an edgy side. It was shown in Arrma's LSD assembly video on Youtube, but I have no idea if that has anything to do with the notchiness.

 

[nyev]

Thanks, all makes sense now. Yes, I'm aware of the direction/orientation of the LSD plates, where the sharper edge is supposed to face outwards on either side. Not sure why that is, but definitely have been following that advice from Arrma. I've also noticed the slightest bit of variance in the LSD plates themselves, where the outer edges can be warped one way or the other. But these are flexible and I don't think that is really making a difference. I think you are right in that the notchiness is purely a psychological effect. Getting to the root of it is totally an OCD-driven quest for understanding what it happening. Now that I feel I've figured out the cause (slight difference in diff cup depth), I can move on with my build/M2C upgrades, etc! As a plus I now feel like I understand far more about how the diffs work and are assembled.