Kagama Me killing my Kagama rear diffs

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trippinmunky

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Corally RC's
  1. Kagama
Hi,

So I got a Kagama second hand and soon after I got it there was a clicking noise on acceleration, AI told me I had chipped a tooth on the rear diff, I took it apart and it was correct, a complete tooth totally gone
20261011_204759.webp

so I ordered a new part and then about 20 mins into the first run after fitting it it was clicking again, I carried on for a while longer and it got worse so stopped (maybe should have stopped immediately...)
Got home took the diff apart and this time I have partly chipped a lot of teeth
20261011_204813.webp


So do I need to replace the other gear that this meshes with? Always replace as a pair?

I was doing some small jumps but pretty sure I didn't have the accelerator on full when landing, normally brake a little as I have this reaction of seeing the nose dip and wanting to push the control forwards to brake for some reason

I just remembered that when I removed the diffs there were these what I presume are shims around the diff, but they didnt look the correct size so I didnt put them back on when I rebuilt the diff
20261011_233001.webp


I have 30k, 500k, 20k
I didnt have any 10k, but will order some when I get my new gears

What else do I need to do to stop this continually happening?
Shims?
Metal diff case?

Thanks
 
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1. Yes you need to replace the other gear, called the pinion with a spur.
2. Replace or at least inspect the bearings that support the pinion and the diff. 4 bearings in total.
3. Then you will need to shim the diff to a achieve the proper mesh.

A properly set up corally diff is nearly indestructible. If you are still breaking them then you are going to have to stop abusing the vehicle or get comfortable replacing parts on a frequent basis.
 
Definitely buy legit steel pinion and crown. Strip down the transmission case. I suspect there may be foreign object debris inside your casing. Remove all trace - otherwise this will happen again and again.

Setting the mesh:
  • Too tight - the crown gear needs to be moved away from the input pinion with shims behind the bearing on the opposite side to crown gear
  • Too loose - the crown gear needs to be moved closer to the pinion, by placing shims behind the bearing on the crown wheel side
Mesh between the pinion and crown should not be tight, but - there should be zero backlash.

52329.webp


13 x 16 x 0.1 or 0.2 can set the side to side position of the diff. How many shims you need depends entirely on your transmission case and your gear mesh. It could be none - or up to 3.

Shims serve 2 purposes in this instance:
  • Set the position of the crown relative to the pinion
  • Removes any side to side movement of the diff within the casing
You can also set the position of the input pinion using 6 x 11 x 0.2 shims.

Hope this helps.
 
The bearing on the ring gear side of the diff is often the first to fail. When this happens, the mesh is lost and the gears are susceptible to failure. Inspect often.

Again corally diffs are strong. The quality is up there with my Tekno and Kyosho diffs.
 
Also possibly cracked diff housing, too thick center diff oil in addition to the other tips
 
As others have said while you got it all out check both bearings on the input pinion as well, I did not do this first time around swapping my worn rear diff gears they went bang not long after and had to strip it down all over again 😭.

If you shim the rear input pinion I found if you stick the shim behind the bearing to push it forward, when the shim was fitted behind the rear input pinion the shape of the shaft / gear worn the shim down real fast.

Hope that made sense :).
 
Thanks for everyones replies, really helpful

The crown that I bought last time was a legit Corally part.
I removed, what I now realise are, the shims because they weren't on the diagram in the manual and they don't seem to be the correct size anyway

If I replace the bearings am I ok to replace with TC parts or are there better ones? I don't mind spending more money now to not have to strip it down again so soon

When putting the shims on the crown, how do you test if its a good fit?
If I don't put the case back on so I can see the gear mesh then it won't stay it place if I turn the wheels or motor will it?
and if I put the case on to hold everything in position then I can't see the gears mesh
 
Partydaz said:
As others have said while you got it all out check both bearings on the input pinion as well, I did not do this first time around swapping my worn rear diff gears they went bang not long after and had to strip it down all over again 😭.

If you shim the rear input pinion I found if you stick the shim behind the bearing to push it forward, when the shim was fitted behind the rear input pinion the shape of the shaft / gear worn the shim down real fast.

Hope that made sense :).
Click to expand...

So put the shim between the case and the bearing

NOT

between the bearing and pinion?
 
Arrrhhh thanks, I hadn't taken the entire gearbox out yet
I wish there was a voiceover on video 2 as to what exactly he is doing and checking for but I will watch it a few more times

Is it worth upgrading to the metal gearbox case or the xtreme diff case while I am taking everything apart?

As a first timer it seems a bit odd to me they don't mention the need for shims in the manual at all, but I did just notice on page 2 "for better performance, some adjustments may be necessary" which is nice and vague..... 🤣 🤣 🤣
 
trippinmunky said:
Thanks for everyones replies, really helpful

The crown that I bought last time was a legit Corally part.
I removed, what I now realise are, the shims because they weren't on the diagram in the manual and they don't seem to be the correct size anyway

If I replace the bearings am I ok to replace with TC parts or are there better ones? I don't mind spending more money now to not have to strip it down again so soon

When putting the shims on the crown, how do you test if its a good fit?
If I don't put the case back on so I can see the gear mesh then it won't stay it place if I turn the wheels or motor will it?
and if I put the case on to hold everything in position then I can't see the gears mesh
Click to expand...
If you replace bearings, ensure they are rubber sealed. 👍

Hybrid ceramic bearings would be nice on driveline components and are highly resistant to corrosion. 🤩
 
If I buy a brand new Kagama will I need to check and add shims to the diffs?

I'm considering buying a new Kagama and using this one for parts to save me some work :)
 
Shimmed from the factory so should be good. But diffs can sometimes leak during shipping so it’s good to check the diff fluid levels before running
 
trippinmunky said:
Thanks for everyones replies, really helpful

The crown that I bought last time was a legit Corally part.
I removed, what I now realise are, the shims because they weren't on the diagram in the manual and they don't seem to be the correct size anyway

If I replace the bearings am I ok to replace with TC parts or are there better ones? I don't mind spending more money now to not have to strip it down again so soon

When putting the shims on the crown, how do you test if its a good fit?
If I don't put the case back on so I can see the gear mesh then it won't stay it place if I turn the wheels or motor will it?
and if I put the case on to hold everything in position then I can't see the gears mesh
Click to expand...
The shims are mandatory, if you removed them you will kill a diff, especially the rear diff, extremely fast. When setting mesh using shims, there is no really great way to explain it. Try to watch videos and give it your best. If you end up buying a new Kagama while using the current one for a spare, you can practice with that. The main thing to remember is that the gearbox should rotate smoothly for an entire rotation when done.
 
trippinmunky said:
So put the shim between the case and the bearing

NOT

between the bearing and pinion?
Click to expand...
Yes between the case and the bearing :).

I have the extreme metal diff cases in my Kagama 6s as the rear one would leak all the bloody time and the sexy team corally extreme aluminum ones have been bullet proof no leaks at all after a good summer of abuse.

Cheaper option but just as good is the ADU version, got them on my syncro 4 lovely bit of kit:
https://www.aliexpress.com/item/1005007327636174.html?pdp_npi=4@dis!GBP!￡14.08!￡13.66!!!121.13!117.52!@210389a017918241144291174e0d44!12000040282510527!sh!GB!0!X&spm=a1z65.store_weex_home.shop_wireless_search_module.1005007327636174.
 
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👆 Yes exactly. It shouldn't have backlash in the mesh. Obviously diffs shouldn't have side to side float either.

There isn't an exact number of shims from build to build because it depends entirely on the mouldings and fit that day. Example: it might be one shim per side, 2 shims on the opposite side - or even no shims if the casings work out a tad on the smaller side of the tolerances.

It should be smooth, no binding and no 'tick of play' either. Basically with a light layer of grease - no play. No tight spots. 0.1 and 0.2 shims are your friends. 👍

Please also bear in mind the best shimmed gears in the world still aren't going to prevent huge torque/inertia twisting the cases if you do crazy stuff. In that case, 7075 is your friend. It's also machined to much finer tolerance. 👍
 
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