Kraton Diff Outdrive broke and damaged lower Suspension arm

[Mr.WaCko]

Dear Arrma fans,

Spend some time running my new Kraton EXB after a number of sand dune runs over a number of weekends I've had my fair share of issues with the EXB (not so Arrma though)

1. Broken wing mount and wing mount screws
2. A shim popped out of the rear diff case and landed on the dogbone
3. Broke a 10T pinion in half
4. Broke my front left diff outdrive after a small jump on a sand dune and stripped out part of the plastic of the lower suspension arm (see foto)

Any thoughts on how this might have happened and what I need to do to prevent this from happening in the future
Any special setup I need to take into account to run the Kraton in the sand dunes?

thanks for your support and thoughts on this topic

 

[RCBro80]

Funny... Same thing happened in AMain's latest YouTube vid about that EXB. Wonder if the outdrives can't handle certain power systems and if this is just the next weak spot in the drivetrain?

Time for M2C?

 

[jondilly1974]

The EXB outdrives are harder, which means less wear, but at the cost of being brittle. Try the M2C outdrives instead.

 

[RCBro80]

The EXB outdrives are harder, which means less wear, but at the cost of being brittle. Try the M2C outdrives instead.

Interesting, I had no idea. Good to know!

 

[Mr.WaCko]

The EXB outdrives are harder, which means less wear, but at the cost of being brittle. Try the M2C outdrives instead.

Ok so no change in setup needed for sand dunes, just parts?

 

[SrC]

How does a shim pop out of the Bulkhead????
Are you sure it wasn't a popped out Bearing seal that you see there.???????????
Sand can put a lot of load on the drivetrain for what it is worth. Sand will wear out more moving parts than you think. It will pack into the output cups etc. Maybe rethink where you bash.
M2C if they have those EXB diff out drive cups. I swear by the M2C v4 ones.

 

[Mr.WaCko]

How does a shim pop out of the Bulkhead????
Are you sure it wasn't a popped out Bearing seal that you see there.???????????
Sand can put a lot of load on the drivetrain for what it is worth. Sand will wear out more moving parts than you think. It will pack into the output cups etc. Maybe rethink where you bash.
M2C if they have those EXB diff out drive cups. I swear by the M2C v4 ones.

On the shim, I have no clue it was really missing inside the diff case on the left hand side on the rear.
I am looking for other spots where to bash but the sand makes for a great bashing terrain haven't found any alternative close by just yet. Running it on a concrete/steel skate park doesn't seem to be the best for the car either

 

[L3phturn]

Did you set your droop screws so that the suspension doesn’t hang on the shock shafts at full extension?

 

[Mr.WaCko]

Did you set your droop screws so that the suspension doesn’t hang on the shock shafts at full extension?

To this part I am new do you have any video/photos explaining what to set and how to set it?

 

[L3phturn]

To this part I am new do you have any video/photos explaining what to set and how to set it?

The short answer is to set the droop screws so that you have to compress the shocks just a bit to connect them at full extension. I do this by setting the truck up on a stand, wheels off, and taking the pins out that connect the shocks to the A arms. Then I will adjust droop so that I need to compress the shock a bit in order to get the pin in to connect it. I'll measure both sides to try and ensure they are even, but you can just eyeball it.

One thing I haven't heard people mention is that they fixed the droop screws on the EXB. The 6S platform used to have a droop screw that adjusted from the top with the end of the screw shaft contacting the chassis ears, but that wore holes in the chassis. The EXB has flipped the screws over so the round button head contacts the chassis ears so it doesn't dig in like that. It's much better. Did they also do that on the new V5s?

This video is pretty good:

Also a good video:

 

[Notorious J]

I've had no issues with the outdrives on my EXB and I've sent it 25 feet up and 50 feet forward. Weakness is in the rear arms, but definitely not the outdrives. The pins on my rear driveshafts are actually showing signs of wear (flat spots on the pins) so the outdrive cups are doing exactly what they were meant to do.

 

[jondilly1974]

I've had no issues with the outdrives on my EXB and I've sent it 25 feet up and 50 feet forward. Weakness is in the rear arms, but definitely not the outdrives. The pins on my rear driveshafts are actually showing signs of wear (flat spots on the pins) so the outdrive cups are doing exactly what they were meant to do.

I have two outdrives that needed replaced. One oddly warped and couldn’t get a shim over it. I could have filed it down, but just replaced instead as I have spares. The other broke clean as shown here as a stone got stuck between the output cup and the arm. Neither of these are examples of extreme flaws, but enough for me to spend a few $$ more for the M2C versions instead. I still have them in a bag waiting for the next failure.

 

[SrC]

On the shim, I have no clue it was really missing inside the diff case on the left hand side on the rear.
I am looking for other spots where to bash but the sand makes for a great bashing terrain haven't found any alternative close by just yet. Running it on a concrete/steel skate park doesn't seem to be the best for the car either

Yeah, I agree, bashing on cement is not my thing. Tears up/gouges the chassis and body at best and bends chassis worse case. I usually go to a baseball field with low cut grass on the infield and jump the pitcher mounds, run the bases with my 11 yo son and his Noto. etc. My BB fields have mounds of clay for field and P. mound maintenance. I get some big air on that also. Sand can be forgiving impact wise, but can really screw up the drivetrain especially if it is very loose and deep sand. I been to my beach a few times. Man my drivetrain was trashed in several packs. These Arrma's don't have sealed input and output drives, (no boots/seals around them) Sand also does an number on the spur and pin.

 

[Mr.WaCko]

The short answer is to set the droop screws so that you have to compress the shocks just a bit to connect them at full extension. I do this by setting the truck up on a stand, wheels off, and taking the pins out that connect the shocks to the A arms. Then I will adjust droop so that I need to compress the shock a bit in order to get the pin in to connect it. I'll measure both sides to try and ensure they are even, but you can just eyeball it.

One thing I haven't heard people mention is that they fixed the droop screws on the EXB. The 6S platform used to have a droop screw that adjusted from the top with the end of the screw shaft contacting the chassis ears, but that wore holes in the chassis. The EXB has flipped the screws over so the round button head contacts the chassis ears so it doesn't dig in like that. It's much better. Did they also do that on the new V5s?

This video is pretty good:

Also a good video:

Thx for sharing this very insightful
Interestingly though as I run my car on sand dunes and jump it a lot as well the droop would actually have to increase instead of running it more tight as it would stiffen up the entire truck. But from what I've been reading in this post people recommend to run less droop to prevent my diff outdrives from cracking open, hmm confusing

 

[L3phturn]

Thx for sharing this very insightful
Interestingly though as I run my car on sand dunes and jump it a lot as well the droop would actually have to increase instead of running it more tight as it would stiffen up the entire truck. But from what I've been reading in this post people recommend to run less droop to prevent my diff outdrives from cracking open, hmm confusing

You aren’t running less suspension travel, you are just eliminating undamped slop at the end of the travel. You are preventing the suspension from hanging on the shock shafts. The spring rate is still the same, you just tighten the droop enough that when you jump it doesn’t yank on the shocks. It won’t change your ride height, spring rate, or damping at all. The only change will be how far your wheels can drop into a depression or when jumping, and it won’t change that much. You just want it so that the droop screws stop it, not the shock shafts.

 

[Mr.WaCko]

You aren’t running less suspension travel, you are just eliminating undamped slop at the end of the travel. You are preventing the suspension from hanging on the shock shafts. The spring rate is still the same, you just tighten the droop enough that when you jump it doesn’t yank on the shocks. It won’t change your ride height, spring rate, or damping at all. The only change will be how far your wheels can drop into a depression or when jumping, and it won’t change that much. You just want it so that the droop screws stop it, not the shock shafts.

Thanks for that clarification

 

[nomis38]

I really feel like it would take some binding to do this. Ive had and seen a lot of outdrives in use. Lol I don't know hundreds maybe thousands. Not seen one blow up like that.

 

[Mr.WaCko]

I really feel like it would take some binding to do this. Ive had and seen a lot of outdrives in use. Lol I don't know hundreds maybe thousands. Not seen one blow up like that.

Probably I am suffering from a language gap here. What do you mean with 'take some binding to do this'

 

[nomis38]

I meant the shaft was getting stuck in groves in the cups and caused it to have 0 flex so something had to give.

Dogbones and cups are a very sloppy but effective way to transfer power to our rc tires.

After a while the pin at the end of the dogbone wears a groove in the cup. If the groves are worn just right the shaft can become stuck so to say. And the next time you land hard the shaft has nowhere to go.

Hopefully that makes sense.

 

[Mr.WaCko]

I meant the shaft was getting stuck in groves in the cups and caused it to have 0 flex so something had to give.

Dogbones and cups are a very sloppy but effective way to transfer power to our rc tires.

After a while the pin at the end of the dogbone wears a groove in the cup. If the groves are worn just right the shaft can become stuck so to say. And the next time you land hard the shaft has nowhere to go.

Hopefully that makes sense.

That makes sense indeed, thanks for clarifying. Wondering how fast this process goes as I have ran my cars around 10 - 12 packs of 6s. To me that would sound/feel like soon to see wear and tear after a limited number of runs