I've read they are supposed to behave similar to a Torsen diff, but not identical. I'm using mine and they work fine, that's not the question here.

Looking at the internals they are more like a normal diff but they have these extra 4 square pices with a hole for the gears. I don't understand how they would work different than a normal diff.
Can anyone explain how they actually work?

those squares with the holes actually clamp the planetary gears and "lock" the diff when there is grip at both sides, when grip is lost at one side it will still "diff out" like a regular diff!
this means the Kyosho TCD is basically a powerlock diff that locks up inder power when there is grip but diffs out when there isn't, due to irs nature its self adjusting to the grip levels available so you wont have to mess about changing oils etc
they are mainly used in the front as "off power" they are very free which should give good turn in & then lock up under power on the corner exit providing plenty of drive or pull out of the corner.
some people say they are better on smoother high grip tracks BUT are a little inconsistent in their "feel" on bumpy, rough tracks so they prefer to run 3 regular diffs all round instead
if you already have one then try it but if you gotta buy one then i'd spend the money on getting some different oils & just do some testing to find a good setup that way

I already have them in both buggies. Just trying to figure out how they work.
Sounds like they do not work like a torsen as many have said. The torsen gives power to the wheel with most grip.

Thank you for explaining even if I still don't understand how the squares can lock the diff.

edit:
Hmmm, I think I got it. They don't actually lock up but since the gear is in the hole the viscosity of the oil makes it 'lock-up'. The normal diff has more space between the gear and housing not allowing the oil to lock it.


edit again:
Even I have a hard time to understand what I wrote. Ebonics here I come .....

think of it another way
the diff is turned by the big gear aroiund the outside
therefore the casing is turning the gears
the squares with the holes are turned by the casing and they surround the gears which are a close fit inside them
sideways force on the squares with the holes, pushing agains the gears that are inside them causes friction between the gear & the square with the hole
the more grip the more friction is created & the more it locks]

have a closer look at the diffs & you should see what i mean

thnaks showtime, saved me a lot of effort in having to reply when i read what u wrote. u explained it perfectly.

Got it.

yay

its a tricky thing to try & explain but if you are familiar with the insides of those diffs or at least have a detailed drawing of one to hand you should be able to get your head round it

they are OK but not really any better than a std diff with the right weight silicone

I should take a closer look next time I'm rebuilding them..... which leads to the next question.

Where do I get the correct oil for them now? I need the red oil that comes with the kit but haven't seen it on-line in quite some time now.

you can use good ole ATF



Automatic Transmission Fluid

OK, let see here.

When off power: The diff will run as a normal diff would, either wheel rotating at their own speed.

On Power: The blocks act in a way similar to runing thick oil in the diff. The blocks dont move, the gears dont bind. But the presence of the blocks around the planetary gears means that the oil doesn't have the room to move that it would in a stock diff. This lack of flow around the gears locks up the diff, it still slips a bit between sides but if you were to try and hold a wheel still, you'd struggle, as opposed to a stock diff where the other wheel would just spin twice as fast.

we've already expained how they work or did you miss that bit

its not the oil that locks the diff its friction between the blocks & the planetary gears!
i'll find a pic to post i'm sure i have one somewhere!

pic below, obviously the TCD's are the left diff & centre diff in this pic