Kraton K4s 2.5 sounds different after a crash. Where should I dig?

[Barmaleus]

Hi all!

Had a nasty crash with my Kraton 4s v2.5. After that, the car started to sounded different, though drove fine. Hard to explain the difference, but you can briefly hear it at the end of this video (the car sounds "normal" until I crash at the last jump).

Spoiler: Video

Visually no parts are broken. Links, steering, shocks, etc., everything looks intact.
I've disassembled the car and to me, front/rear diffs sound and feel fine. The suspect is the center diff. I've recorded a video for anyone willing to help me troubleshoot.

Spoiler: Video

So far the main problems I see (but I don't know if these were caused by the crash):
1. Pinion gear was absolutely loose. I will of course tighten the grub screw. But it looks like there is so much play... Should I replace the pinion gear, perhaps? So that it sits tight even without the grub screw.
2. The spur gear has quite some play. Should it be like that or it must be tight?

Have not looked into the diff itself yet.

Thank you for any comments/ideas.

 

[parcou]

I do not have this model... Your front and rear diffs sound normal and good. Certainly the power module you have in hand I feel the spur should not be moving. Correct, the pinion gear should NOT move...those two items need to be addressed.

Good video!

 

[Tex Koder]

Hi all!

Had a nasty crash with my Kraton 4s v2.5. After that, the car started to sounded different, though drove fine. Hard to explain the difference, but you can briefly hear it at the end of this video (the car sounds "normal" until I crash at the last jump).

Spoiler: Video

Visually no parts are broken. Links, steering, shocks, etc., everything looks intact.
I've disassembled the car and to me, front/rear diffs sound and feel fine. The suspect is the center diff. I've recorded a video for anyone willing to help me troubleshoot.

Spoiler: Video

So far the main problems I see (but I don't know if these were caused by the crash):
1. Pinion gear was absolutely loose. I will of course tighten the grub screw. But it looks like there is so much play... Should I replace the pinion gear, perhaps? So that it sits tight even without the grub screw.
2. The spur gear has quite some play. Should it be like that or it must be tight?

Have not looked into the diff itself yet.

Thank you for any comments/ideas.

From your second video, it's obvious BOTH your pinion gear AND your center diff housing are loose.

Must tighten the grub screw in your pinion gear And your center diff ,Pronto!

You will need to re-check the fluid in your diff, it's leaked out some ,if not all.

 

[Barmaleus]

Thank you guys! Will tighten all up and check the diff fluid.

Also, lifehack. The diff "holder/blocker" part did not want to move. Zip tie to the rescue! Super easy to pull that part out.

 

[332_RC]

Thank you guys! Will tighten all up and check the diff fluid.

Also, lifehack. The diff "holder/blocker" part did not want to move. Zip tie to the rescue! Super easy to pull that part out.

View attachment 363668

10-4. I just put a 4s fluid center diff & power module in my 3s Senton. Fit right in easy. Great hack.

 

[Barmaleus]

10-4

That some Morse Code, sir?

 

[332_RC]

That some Morse Code, sir?

It means I hear ya or I got it. Old CB radio thing. It's a

 

[Glitch]

Hi all!

Had a nasty crash with my Kraton 4s v2.5. After that, the car started to sounded different, though drove fine. Hard to explain the difference, but you can briefly hear it at the end of this video (the car sounds "normal" until I crash at the last jump).

Spoiler: Video

Visually no parts are broken. Links, steering, shocks, etc., everything looks intact.
I've disassembled the car and to me, front/rear diffs sound and feel fine. The suspect is the center diff. I've recorded a video for anyone willing to help me troubleshoot.

Spoiler: Video

So far the main problems I see (but I don't know if these were caused by the crash):
1. Pinion gear was absolutely loose. I will of course tighten the grub screw. But it looks like there is so much play... Should I replace the pinion gear, perhaps? So that it sits tight even without the grub screw.
2. The spur gear has quite some play. Should it be like that or it must be tight?

Have not looked into the diff itself yet.

Thank you for any comments/ideas.

The whole issue is definitely the spur and pinion, both are damaged. I would try to upgrade/replace both

The whole issue is definitely the spur and pinion, both are damaged. I would try to upgrade/replace both

Definitely try tightening stuff first. But if you tighten it down and it still has play, it needs to be replaced

 

[Barmaleus]

It means I hear ya or I got it. Old CB radio thing. It's a

Ahh, I see.
10-2

The whole issue is definitely the spur and pinion, both are damaged. I would try to upgrade/replace both


Definitely try tightening stuff first. But if you tighten it down and it still has play, it needs to be replaced

Thank you! Will follow this plan

 

[Jon NC RC]

Hi all!

Had a nasty crash with my Kraton 4s v2.5. After that, the car started to sounded different, though drove fine. Hard to explain the difference, but you can briefly hear it at the end of this video (the car sounds "normal" until I crash at the last jump).

Spoiler: Video

Visually no parts are broken. Links, steering, shocks, etc., everything looks intact.
I've disassembled the car and to me, front/rear diffs sound and feel fine. The suspect is the center diff. I've recorded a video for anyone willing to help me troubleshoot.

Spoiler: Video

So far the main problems I see (but I don't know if these were caused by the crash):
1. Pinion gear was absolutely loose. I will of course tighten the grub screw. But it looks like there is so much play... Should I replace the pinion gear, perhaps? So that it sits tight even without the grub screw.
2. The spur gear has quite some play. Should it be like that or it must be tight?

Have not looked into the diff itself yet.

Thank you for any comments/ideas.

Congrats !! You found the problem...... Videos are great to help the forum problem solve....

 

[EOTR]

I have the exact model as you. As previously mentioned by the members above, the pinion gear should NOT have any movement. Once you tighten it down again, (use some loctite if you have some) be sure and put in the e-clip, too. Same goes for the ring gear. NO movement. I ordered and just rec'd a couple of replacement parts in case something like this happens to me. I will use them only if required. It looks like your ring gear has got some above normal wear and tear. Perhaps the pinion wasn't meshed properly with it. Another point: when you go to refill your diff, be sure it is assembled properly. Keep in mind that the exploded view has Part #AR709067 and Part #ARA716034 in reverse order. The rubber O-ring (ARA716034) MUST go against the diff housing first (there is a machined recessed slot that it fits into ) in order to prevent leakage of your diff fluid. I have sent a photo of these two incorrectly displayed parts. Good luck. Let us knows how you progress.
** Now that our winter has subsided enough, I actually had my Kraton out just the other day for it's inaugural run. FINALLY!! Although I was just 'testing' it out on the front street, so far, so good. **

 

[Barmaleus]

@EOTR Thanks a lot for commenting!

and put in the e-clip, too

That's funny. There was NO e-clip when I opened the diff case yesterday. I just looked at an old photo (below) taken in Feb this year: the e-clip was there! Wow. Not sure what to say

It seems the pinion gear has been wobbling there for quite some time already. I assume it must sit tight even without the grub screw. And it does not, sadly. I'll go to a local RC shop to see if they have a good replacement.
Thanks for the links to upgrade parts, useful!

Another point: when you go to refill your diff, be sure it is assembled properly. Keep in mind that the exploded view has Part #AR709067 and Part #ARA716034 in reverse order. The rubber O-ring (ARA716034) MUST go against the diff housing first (there is a machined recessed slot that it fits into ) in order to prevent leakage of your diff fluid. I have sent a photo of these two incorrectly displayed parts.

Thanks a lot, I'll pay attention to it!

** Now that our winter has subsided enough, I actually had my Kraton out just the other day for it's inaugural run. FINALLY!! Although I was just 'testing' it out on the front street, so far, so good. **

Ahh, wonderful =) Glad the first bash was a success! Onwards to more blasting! =)

 

[Dales396lt4]

If you have it apart check the bearings, one of mine on the center diff. was bad. It felt kind of crunchy.

 

[Barmaleus]

@Dales396lt4 Yeah, will do!

 

[Barmaleus]

Welp, one of the bearings that holds the diff case... Will replace both =)

 

[Barmaleus]

Also. Upon further inspection, it looks like the pinion gear has a crack in it. Damn =)

 

[Dales396lt4]

And no threads! I would replace with a 14T or a 15T. I liked the stock 2400KV motor on a 15T.

 

[Barmaleus]

And no threads! I would replace with a 14T or a 15T. I liked the stock 2400KV motor on a 15T.

The thread is alright. Just a strange camera effect.
In any case, will have to replace it asap.
What does increasing the nr of teeth do? Car goes faster?

 

[Dales396lt4]

Yes, But it comes will a cost, Heat. I did not have a problem with the 15T and it ran great! You will need to check motor an ESC temp after you run it. The 15t is not for tall grass it will overheat it. So how do you run your car? dirt, street, short grass

 

[Barmaleus]

@Dales396lt4 Mostly grass/hard soil/small rocks. Actually pretty happy with the current speed. Plenty for learning