Kraton V4 center diff build

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mitch at m2c mentioned something awhile back about hooking a drill to your diff ..I did it to my kraton diffs dry only ran it long enough to get the gears hot..

What speed drill and for how long did you do this..??

It sounds like a really good idea, I understand how it would remove all the imperfections on the castings etc.
1) shim, assemble dry, and drill... 2) re-shim, fill with oil, assemble, the end result buttery smooth diff.. win win..???
 
What speed drill and for how long did you do this..??

It sounds like a really good idea, I understand how it would remove all the imperfections on the castings etc.
1) shim, assemble dry, and drill... 2) re-shim, fill with oil, assemble, the end result buttery smooth diff.. win win..???
man tbh I don't think I even looked at the speed settings lol I think I had it maxed out kinda where my big drill stays ..its a ridged 2 speed drill

if you are holding the diff in your hand trust me you will know when to stop it will get to hot to hold lol I just don't know if that long is even necessary yet it's still new to me as well
man tbh I don't think I even looked at the speed settings lol I think I had it maxed out kinda where my big drill stays ..its a ridged 2 speed drill

if you are holding the diff in your hand trust me you will know when to stop it will get to hot to hold lol I just don't know if that long is even necessary yet it's still new to me as well
and I will say the end result is butterfly smooth shockingly
 
So quick question...

Can I run the diff with no shims on the small gears..??

I'm rebuilding the front and rear now, and they seem a bit notchy with the Mugen shim under planet gear and standard Arrma shims under small gears..

I measured the Mugen's planet shim and it is the same thickness as standard Arrma but bigger diameter, I did try with whole Mugen shim kit but I couldn't even turn the diff..?? the small gear Mugen shims seem to be 0.22mm-0.24mm where as the Arrma ones are 0.15mm..

Or could I run one shim on the small gears..?? I was under the impression that you had to have a minimum of one per side, please correct me if I'm wrong..??

Any thoughts..!!???
 
Yes they are the new V4's

Ok. Here is what I would do: Nothing. The new diffs come with 4 shims for the small gears (one on each side of the planetary/satellite gears) and one that goes over the o'ring and under the pin and sun gears (2). I honestly don't think it needs any more on the inside. Plus you have two more small ones for each outdrive. The V3 diffs didn't come with a shim for under the sun gears (big gears), so I used to add those. Once I tried adding a additional shim to one side of the planetary gears (I say additional because they came with shims for those gears like the V4's). It bound up my diff. I think the V4 diffs are fine as they are. Definitely do not add additional shims to the planetary/satellite gears. If you want to use the big one under the sun gears, remove the stock ones that are already there.
 
I had removed the stock small one under the planet gear and replaced it with a Mugen bigger in diameter but no thicker..

All the rest are of stock size etc, but it still binds up...??

I'm going to put it back to completely stock and see what happens.. then test again..!!

The crazy thing is though is the centre one needed extra shims under the small gears like a V3..!!...?
 
I had removed the stock small one under the planet gear and replaced it with a Mugen bigger in diameter but no thicker..

All the rest are of stock size etc, but it still binds up...??

I'm going to put it back to completely stock and see what happens.. then test again..!!

The crazy thing is though is the centre one needed extra shims under the small gears like a V3..!!...?

When you sat extra shims under the small gears like the V3, are you talking about the 4 satellite/planetary gears? I'm confused because there is no "under" on those. And if so, like I said before, I never had to add shims there in my V3's.
 
On the centre diff it ended up being.. the full Mugen shim set 1 big on each planet, 1 on each small + 2 extra Arrma shims on the small gears.

so total of 6 small and 2 big..?? hope that makes sense..
 
On the centre diff it ended up being.. the full Mugen shim set 1 big on each planet, 1 on each small + 2 extra Arrma shims on the small gears.

so total of 6 small and 2 big..?? hope that makes sense..
Clear as mud ?

Sun gear = the two big gears that go in the bottom of the diff cup and the inside of the diff top/ring gear. You can refer to it as the big gear. New V4's come with a shim that sits under each one. V3's didn't have a shim under them and people would add one of the MS big blue ones under each.

Planetary gears are the 4 small gears. You can call them the small gears. In both the V3 and the V4 each one has a factory shim between them and the cross pin holder. In the videos I've seem people will add an additional shim to one of the two on each cross pin. You then have two small gears with 2 shims (factory and additional) and two with just one shim (factory). In the V3 a total of 4 shims would be added. Follow?

Look, at the end of the day if it works for you then no worries. I have had nothing but V3 diffs and all I have ever done was add big shims to the big gears that didn't have them. That's it. I tried adding shims to the factory ones on the planetary gears and it became too tight. Also, all of this internal shimming is for the benefit of the internal gears. How many "I broke my planetary/sun gear threads do you see? ? Sure there are a few and it almost always happens by landing under load. You can shim them nine ways to Sunday and if you land full throttle they will gernade.

I truly feel that the V3 and newer diffs are made to a stricter standard than previous versions and they really don't require much shimming at all. I didn't even shim my Talion diffs and I send it all the time. No exploding gears ?
 
Clear as mud ?

Sun gear = the two big gears that go in the bottom of the diff cup and the inside of the diff top/ring gear. You can refer to it as the big gear. New V4's come with a shim that sits under each one. V3's didn't have a shim under them and people would add one of the MS big blue ones under each.

Planetary gears are the 4 small gears. You can call them the small gears. In both the V3 and the V4 each one has a factory shim between them and the cross pin holder. In the videos I've seem people will add an additional shim to one of the two on each cross pin. You then have two small gears with 2 shims (factory and additional) and two with just one shim (factory). In the V3 a total of 4 shims would be added. Follow?

What you said is what I've got..??? some slight changes my end, but like you say whatever works..???
 
So here are the final diffs, center was 6 x Mugen ( 2 big 4 small ) + 2 x Arrma shims, the front and rear used all stock shims except I swapped in 1 Mugen 18mm under the big gear in each diff..??

IMG_2547.jpg
IMG_2536.jpg
IMG_2549.jpeg


Finally got round to grinding the edges of the cups too...?

IMG_2533.jpeg


Part numbers..?? ( Thx @Rich Duperbash for the Mugen part number )

IMG_2515.jpeg
 
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I found it handy to just add one or two extra gaskets depending on the type factory or not to some diffs vs taking it apart and finding out what shim wasnt needed ... don't work every time but if it works for you try it out I havnt had any issues so far
 
In the end... it doesn't really matter what everyone does. Shimming is done to take up slop/imperfections in machining or to take up slop caused on purpose by the mold or machining to end up with proper gear lash.

You shim until it feels nice and smooth without any binding when dry. If it binds, remove a shim or use thinner shims. If it doesn't bind, shim until it does, then remove one until it doesn't.

Personally, I try to at the very least use shims under the large sun gears to cover the o-ring on the outputs so the pin itself isn't rubbing on the o-ring. If those are the only 2 shims that fit while still not having binding, then that's all I'd run.

As it was, on my outcast, I ran whatever was in it for 2-3 bash sessions because I was waiting for shims/oil to be delivered. So my gears were "worn in" by the time I pulled them apart. I used the full mugen shim kit on my 2018 outcast and they spun nice and smooth when dry. One under each of the 4 planetary gears and one under each sun gear. I then added 3-4 shims (tamiya I think) on the outside of the ring gear side bearing to set the gear lash on the ring/pinion.


This should be a sticky, he could not have explained it any better, shim dry, smooth,no binding.

YT has a lot of diff shims, check also airsoft gearbox shimming, at least it gives an idea what to look for when doing them.

Adam Drake shim diff videos are great.
 
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