Kraton Arrma Kraton EXB (Blown Rear Differential)

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I'm undecided. I'm running the 30k because I've seen a lot of guys recommending 20k in the rear, and 30k was the closest I could find. I'm not that experienced of a driver yet to know the difference. Maybe if I switched it out to the 5k I could report back more accurately. It does "hook up" pretty hard, but I'm not sure if that's because of my motor and tire combo or because of the diff fluid. Thoughts?

I think 30K is recommended for an open rear diff, but if you've changed it to an LSD rear diff the fluid should be thinner.
 
I'm undecided. I'm running the 30k because I've seen a lot of guys recommending 20k in the rear, and 30k was the closest I could find. I'm not that experienced of a driver yet to know the difference. Maybe if I switched it out to the 5k I could report back more accurately. It does "hook up" pretty hard, but I'm not sure if that's because of my motor and tire combo or because of the diff fluid. Thoughts?
For me when the rear is too locked it drifts around turns under power (oversteer) and spins out. Any amount of power in a turn and it just spins. Used to be I could make it do that with enough input but mild input would allow me to make a turn without losing the rear end.
 
I think 30K is recommended for an open rear diff, but if you've changed it to an LSD rear diff the fluid should be thinner.

This is good to know. What do you recommend in the rear, assuming it’s LSD?
 
For me when the rear is too locked it drifts around turns under power (oversteer) and spins out. Any amount of power in a turn and it just spins. Used to be I could make it do that with enough input but mild input would allow me to make a turn without losing the rear end.

Now I feel like I might notice it since you mentioned it. ?
I would run 10k.

I’ll try it with that and see if I could feel the difference. ??
I've got fully open rear and am running 20k ?

You’re one of the reasons I have 30k in now. ?

20k Hudy wasn’t in stock so I went with 30k. I’m going to try 10k now that I have LSD in the rear; I’ll see how I like it.
 
I would run 10k.

I just put 10k in the rear with LSD per your recommendation. What would you run in the center and front? I currently run 50k in the front and 300k in the center. The only reason I run the 300k is because 200k wasn't available anywhere.
 
I just put 10k in the rear with LSD per your recommendation. What would you run in the center and front? I currently run 50k in the front and 300k in the center. The only reason I run the 300k is because 200k wasn't available anywhere.
Those weights should work. If you have issues with on power steering you might want to go with 30k in the front.
 
Those weights should work. If you have issues with on power steering you might want to go with 30k in the front.

Good to know. I’ll see how it behaves now with the current weights, and I’ll try 30k in the front should I have any issues with the on power steering. Thanks again! (y)
 
I'm aware there are other threads for people who have noted blown rear diffs on their Kraton EXB. I'll share my experience, what caused it to happen and note the potential fix based on what Horizon Hobby told me, as well as the other gracious forum members who have shared their experiences and findings.

Motor: Castle 1717 1650kv
ESC: Mamba Monster X 8S
Pinion: Tekno 23t
Spur Gear: Factory
Battery: 2x Spektrum 3s 100c
Voltage: 7.5V
Tires: Pro-line Bandlands MX38 3.8 (Belted)

Before I ever ran the car I took apart the front, center, and rear diffs to add in Hudy Ultimate Silicone and inspect everything. Thanks to all the forum members who have created threads on the issues with the EXB; it helped me prepare for what could happen with the rear diff.

My Diff Fluid Setup
Front: 50,000cst
Center: 300,000cst (200k wasn't in stock)
Rear: 30,000cst (20k wasn't in stock)

Conditions When The Diff Was Blown
Temperature: 74 degrees fahrenheit
Weather: Clear
Riding surface: Wet grass and Pavement
Riding style: Non-aggressive (feathering the throttle)

As I was riding, I started to hear a clanking noise and so I immediately drove the car into the garage and took apart the diff. Once again, thanks to everyone on this forum posting about their EXB issues, I was able to quickly identify the problem area. As you'll see in the images below, the sun gears cracked and some have also worn down.

I have reached out to Horizon and they are sending me all new diff parts including the LSD plates (ARA310984) that are in the front and center diffs. They said that these plates will resolve the issue. (TBD)

In the meantime, I have won an auction on eBay for a brand new EXB diff. With shipping the grand total was $89.99. To note - I'm super thankful my wife doesn't ask too many questions so long as I'm happy :LOL:. I realized I was raped for paying that much... but I want to get back to bashing and enjoying my car. If it's only $89.99 between me enjoying my car or sitting it on a self, I'd rather shell out the dough.

There isn't a price for the kool-aid smile this car gives me when I'm bashing it. ?

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**UPDATED September 9th, 2020**

So good news - I dissembled the center diff I purchased at a ridiculous price on eBay ?. What I took from it to rebuild my rear diff was the LSD plates, sun gears, planet gears, and one shim. I took one of the thinner (thinest one) shims from that donor diff and put it on the ring gear side of my rear diff; I tried to add one to the diff cup side as well, but it was extremely tight. (that's what he said) ?

Lastly, I filled the diff back up with Hudy 30,000cst Ultimate Silicone Oil.

I did a "light" bashing session last night and it everything was running well. I was using two 3s 100c Spektrum batteries at 7.5V. I'm hoping this can be consider a chalked up issue, but only time will tell. Hopefully, this information helps someone dealing with similar issues. ?
Curious to know whether you have had any more diff issues please? I have the exact same setup as yours and I just broke my front diff as well. I am starting to wonder if these Pro-line MX38’s aren’t the cause. Let me know please.

thanks!
 
Curious to know whether you have had any more diff issues please? I have the exact same setup as yours and I just broke my front diff as well. I am starting to wonder if these Pro-line MX38’s aren’t the cause. Let me know please.

thanks!

After I installed the limited slip plates it never broke again.
 
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