Kraton diff binding no matter what.

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HansDampf

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Arrma RC's
  1. Kraton 4s
stripped the rear diff (not the fist time) and when doing the usual rebuild it seemed extremely tight and notchy, i have done all the normal stuff, moving the shim to the other side, no shim, lessening the yoke a little and its still notchy
the input gear, ring gear and yoke are all new, the binding is in the input and ring
 
Normal when new the sungear teeths are oversized and needs to break in after a few runs its going to spin free again. I used to move the shim to the other side and just made poor gear contact and worn. don't worry about it i once made it super tight and still to this day it has a lot less wear than any other composite diff i had. People will disagree but thats what i learned with those composite diff but DO NOT do this on a metal gear diff it needs to spin without catching
 
Normal when new the sungear teeths are oversized and needs to break in after a few runs its going to spin free again. I used to move the shim to the other side and just made poor gear contact and worn. don't worry about it i once made it super tight and still to this day it has a lot less wear than any other composite diff i had. People will disagree but thats what i learned with those composite diff but DO NOT do this on a metal gear diff it needs to spin without catching
so just stick the shim on the no ring gear side and send it for a bit, can do, just a bit odd that its never happened to me before.
also i saw you in this post and followed some advice there
thanks tho
 
I had the same problem for awhile and it didn’t go away until I replaced the bulkhead/gearbox. Turns out it had taken a hard hit and misshapened it enough to put pressure on the gears.
 
I’d say warped diff cup.
its brand new and my old one is the same
I had the same problem for awhile and it didn’t go away until I replaced the bulkhead/gearbox. Turns out it had taken a hard hit and misshapened it enough to put pressure on the gears.
the thing is it happens when its out the car, so that would not have an impact
 
The 3s line doesn't have diff cups...
They sure do.

98548677-16FA-442A-A389-3AA2D2E1847D.jpeg
 
To me a diff cup is the thing that holds the dogbones lol confusion of words i use ring and pinion for the gears and diff casee
That’s the output cup. ✌?
 
I rather have a notchy diif as it’ll eventually wear in.

The combination of plastic diff cups and cast gears doesn’t help though. Using the ARA220050 diff cups with Mugen gears helps a lot. But I understand that it may not be in everyone’s budget.

When I build my diffs, I lap all gear mating surfaces and shims on 400grit sandpaper and water in a figure-8 motion. This ensures that everything is up to par. I know... I know... seems excessive but devil is in the details.

Also, I like to break-in my diffs. Then again, not many will do this but I swear by it and have never had a diff failure since I started doing the lapping and break-in procedure.
 
I rather have a notchy diif as it’ll eventually wear in.

The combination of plastic diff cups and cast gears doesn’t help though. Using the ARA220050 diff cups with Mugen gears helps a lot. But I understand that it may not be in everyone’s budget.

When I build my diffs, I lap all gear mating surfaces and shims on 400grit sandpaper and water in a figure-8 motion. This ensures that everything is up to par. I know... I know... seems excessive but devil is in the details.

Also, I like to break-in my diffs. Then again, not many will do this but I swear by it and have never had a diff failure since I started doing the lapping and break-in procedure.
A bit confused about the sand paper but i once broke in my kraton for 15mins with new diffs wheels off the ground so far so good?‍♀
 
Lapping (micro-polishing) is done to ensure that backside of metal gears (and shims) are smooth and free of any imperfections/high spots. When done properly, the mating surfaces will have a near-perfect mirror finish which greatly help everything work together. This is also a great way to remove very small amount of material to eliminate the notchy feeling of new diffs.

2DC14788-AD26-47A4-BAC7-95E3B3A18CE4.jpeg
 
Lapping (micro-polishing) is done to ensure that backside of metal gears (and shims) are smooth and free of any imperfections/high spots. When done properly, the mating surfaces will have a near-perfect mirror finish which greatly help everything work together. This is also a great way to remove very small amount of material to eliminate the notchy feeling of new diffs.

View attachment 94833
Mhm interesting but shims arent already flat and polished?
 
Shims we use for our diffs are flat-ish and most often then not, have burrs from stamping process. By lapping them, I get them as flat as possible and eliminate all burrs. Results are worth the effort.
 
Shims we use for our diffs are flat-ish and most often then not, have burrs from stamping process. By lapping them, I get them as flat as possible and eliminate all burrs. Results are worth the effort.
Mhm okay 400 grid sand paper you said? I don't think you will get a shiny finish with that unless you polish with something. Could try but the exb shims are already off of tolerances
 
Mhm okay 400 grid sand paper you said? I don't think you will get a shiny finish with that unless you polish with something. Could try but the exb shims are already off of tolerances

Seeing as I had to explain to you what lapping is, how can you give your opinion? Try it first.
 
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