Kraton Driveshaft Pops Out

[NitroK]

When driving fast over uneven ground, the front right drive shaft came out. Happened twice in the last month and taken a good part of the lower RPM arm with it. Considering limiting the shock travel or shaving 1-2mm from the arm. What could have caused a sudden change?

 

[Eno]

Ditch those RPM arms! Problem solved.

 

[slick2500]

Use stock arms, limit your droop and remove the spacers behind the pillow balls.

 

[Dales396lt4]

Remove spacers behind the pillow balls and I go one step further and take a little off each arm ie (5 or10 strokes each on 220)

 

[Tex Koder]

When driving fast over uneven ground, the front right drive shaft came out. Happened twice in the last month and taken a good part of the lower RPM arm with it. Considering limiting the shock travel or shaving 1-2mm from the arm. What could have caused a sudden change?

View attachment 365637

View attachment 365638

View attachment 365639

The RPM arms are a bit too soft/flexi...

 

[Eno]

Yes they are. Arrma's Jason has spoken out against using the RPM arms. Tekno RC even warns their users of them:

 

[KnowAir]

I agree with what others have said. Remove the spacers from behind the pivot balls. Ditch the RPM lowers, keep the uppers, they seem to hold up better than Arrmas uppers. I feel the Arrma upper arms wear way too fast. They tend to develop a lot of slop at the hinge pin.

 

[332_RC]

Oh no. I've got RPM arms, came on / with that K6 I'm building. I removed the pillow ball shims & I see a visible difference in dogbone engagement, much better, cycling the suspension on the bench. I was going to finally finish it this weekend. Maybe I'll be ok for a while with the RPM arms.

 

[NitroK]

Any difference between Kraton 6s v5 versus EXB arms?

 

[KnowAir]

Oh no. I've got RPM arms, came on / with that K6 I'm building. I removed the pillow ball shims & I see a visible difference in dogbone engagement, much better, cycling the suspension on the bench. I was going to finally finish it this weekend. Maybe I'll be ok for a while with the RPM arms.

Since they're already on it I'd give them a try at least, but if you experience the dogbone issue you know what to do.

I fought this battle a couple years ago with my K6 EXB, stock Arrma arms though. Put spacers on the shock shafts, replaced shock rod ends, even installed Tekno shock rod ends/spring cups.. which are better IMO, but in the end just removing the spacers solved the problem of the dogbones popping out. Also, my stock shock rod ends were pretty hammered, they had a curve in them, one was cracked. I can't imagine that helped my dogbones stay engaged with the diff cups either..

 

[332_RC]

One thing I encountered on this used V3 roller, it had a mix of shock cups. Couple Arrma V3 style & couple, I believe were Teckno or Mugen. They were ok, but not ok. I got the new V5 Mojave HD 6s shock cup ends that are thicker & beefier & bigger ends. I noticed that they moved the spring up 3mm further & the cups sit better in the arms & I've put domed droop screws in & I've adjusted everything out. Seems solid.

 

[KnowAir]

One thing I encountered on this used V3 roller, it had a mix of shock cups. Couple Arrma V3 style & couple, I believe were Teckno or Mugen. They were ok, but not ok. I got the new V5 Mojave HD 6s shock cup ends that are thicker & beefier & bigger ends. I noticed that moved the spring up 3mm & the cups sit better in the arms & I've put domed droop screws in & I've adjusted everything out. Seems solid.

The Tekno cups and rod ends are shorter, so the preload collars had to be threaded down quite a bit to achieve the same preload as the Arrma bits. Also limits how much preload can be added to them. What I do like about the Tekno bits is the "keeper" screw that attaches the cup to the rod end so they can't get knocked off in the "heat of battle". The Tekno hard coated aluminum pivot balls are top notch too vs the Arrma plastic ones. Which I still can't believe Arrma uses BTW. El Cheapo.

 

[332_RC]

The Tekno cups and rod ends are shorter, so the preload collars had to be threaded down quite a bit to achieve the same preload as the Arrma bits. Also limits how much preload can be added to them. What I do like about the Tekno bits is the "keeper" screw that attaches the cup to the rod end so they can't get knocked off in the "heat of battle". The Tekno hard coated aluminum pivot balls are top notch too vs the Arrma plastic ones. Which I still can't believe Arrma uses BTW. El Cheapo.

They weren't Tekno then. No set screw, but did have some type of piece of worn aluminum balls in the lowers that just was all out of wack & loose. Yep, I had to thread the collars up further & the suspension seems better all around.

 

[KnowAir]

Not to get too far off track here but, I would like to see Arrma do better in this area, secured spring perches and steel pivot balls. I see even TRX has stepped up their game on the later models such as the Sledge, Maxx, ect. Too bad they refuse to put on aluminum shock caps though. Unless of course one wants to pay the "ultimate price"!!

 

[Eno]

They tend to develop a lot of slop at the hinge pin.

Bushing them is the answer.

 

[NitroK]

What about the option of adding shims to the CVD as shown below. Any downside?

 

[Dan B.]

What about the option of adding shims to the CVD as shown below. Any downside?
View attachment 365682

I’ve only ever done that to remove play from the outer hub/hex pin, using the shims as thrust washers, basically. Like others have said, remove the a-arm spacers from the balls to remove a couple of mm’s length from the arms and be certain of your droop settings. Limiting shock compression can also help prevent this, as the shaft is often ejected from the cup on full compression, not just at full droop.
And them gosh darned Scorched knuckles shore are purty…

 

[RCbuzz]

Any difference between Kraton 6s v5 versus EXB arms?

They are the same.

 

[KnowAir]

Bushing them is the answer.

I see that in race rigs, my Xray buggy uses steel bushings at the outer pivots, where the hubs are. I don't think we'll ever see that level of detail in an rtr basher. Tekno just started incorporating the bushings with the 2.0 models recently, pretty sure the .3 models never had them. Not positive. I know the V1 MT410 and SCT410.3 don't.

 

[Dan B.]

Also, I was just scrutinizing the first picture you posted above. You most definitely need to limit your shock compression. Your lower a-arm is all chewed up on the top under the cup from contact with the outdrive. I’d bet dollars to donuts that your axles are popping on compression, not extension. I had exactly this same situation with a NOTO that I bought from another forum member. It also came with RPM arms, and they were chewed up in exactly the same place. I tried readjusting droop, pulled the pivot ball rings, and still couldn’t get more than 3 or 4 minutes into a pack without popping out the front right drive shaft.