View Full Version : Ball diff

2002.01.01, 11:52 AM
Just got a Kyosho ball diff and it is HELLA loud! First I had a problem with it clicking and sounding like it was going to come apart while it was moving but I believe that was due to my not having one of the washers in on the side that the wheel hub attaches to with an allen nut. Now it's still VERY noisy while it moves and I can't really get it to operate like my old diff (if I turn one wheel clockwise the other turns counterclockwise) it either is too tight or not tight enough and loud as all hell.

I've played with other diffs and they are silent and smooth as silk, is this a problem with my diff, all kyosho diffs, or is maybe packed with the wrong grease? The car runs fine but is probably twice as loud as it was.


2002.01.01, 12:49 PM
Wow, the ball diff should be very quiet, that sounds very wrong indeed. Have you tried disassembling it and looking at the balls? It was brand new, right? It sounds like it could be defective, you might want to just return it for a new one.

2002.01.01, 01:20 PM

- firstly happy 2002!

I use a Kyosho ball diff and haven't experieced any of the problems you are.

If the wheels are not turning in opposite directions when you turn one wheels, the diff is way too tight or too loose!. If the wheels dont turn at all when you turn the spur gear, it's too loose.
Generally the diff comes assembled and too loose. When tightening, you should tighten the diff in 90 degree incriments.
If it's too tight, the adjustment collar forces the red O-ring into the innards of the ball-dff and the O-ring destroys itself. Fortunately Kyosho do provide more than one O-ring and you can source packets of O-rings that size from most hydraulic/pneumatic suppliers.

What I'd do is strip the ball diff, there is a small circlip that holds the beast together. It can be removed with a precision/jewelers/watchmarkers screwdriver, carefully of course.
The mechanics of a ball diff is quite simple, just dont lose any of the bearings. In fact, Kyosho provide a diagram with the ballidiff.
I suggest a light coating of a lithium/hobby typre grease on the inner parts prior to re-assembly.

Jeff, here is a Thread relating to 'scsi' having a problem with a ball-diff (I still never found out what make he had)


Hope it helps and let us know the outcome :D


2002.01.01, 04:49 PM
Well, I completely disassembled my diff and even went as far as to change the balls out and soaked everything in degreaser to strip out the stock lube. After that, I repacked it with some green diff grease and it's much smoother.

Is it possible to get it to the point where it will spin like the stock diff (ie: one side spins normal and the other side spins reverse) and still lock up enough to drive (how "loose" can the diff be and still be drivable?)

I think I may have overgreased it, unfortunatly Kyosho's instructions neglect how much grease to apply and what type would be best. I'm probably going to see if I can reduce the grease or change it to something different... I didn't put much at all in. It spins much better than it did but it still seems to be either way too tight or too loose.. I gotta screw with it more.

The worst part is that it's VERY loud.. I did a .wav file of what it sounds like that I'm attaching. It starts out slow (you can hear the ESC) and then goes to full throttle, it sounds like the gear mesh is way too tight.

2002.01.01, 06:20 PM
that doesn't sound like the diff's going bad, you're right when you said the gear mesh sounds too tight. Well, is it? What pinion / spacer combination do you have? Is the sound comming from the gears, or the dif, like, when you made the sound file, were you holding 1 wheel stopped, or did you just hold the car up and let both rear wheels spin?

If both rear wheels spun, it wouldn't be the diff's fault. Mabye it's because your pinion gears are worn to match your stock spur gear, and you have to break in your new spur gear on the ball diff. Mabye?? I dunno.


2002.01.01, 06:51 PM

Wow! That sounds hectic!

It seems as if you've examined the obvious causes and nothing much seems wrong.
Are the balls within the diff in good condition, as in round, no flat spots or anything like that? Are the washers on either side in good condition?

Also, as for the grease, well, I dont believe too much can do any harm and I usually just 'coat' the inner mechanism lightly.

I reckon Russ's response makes a lot of sense, perhaps try another pinion gear on your motor.
I didn't have too much mileage on my pinion gear when I installed the ball diff.
It does sound like something is catching or not 'meshing' correctly, but in (personal) opinion, the ball diff doesnt have the complexity to make that much noise!

The spur gear houses the balls which run on smooth washers on either side. I tend to tension my diff to finger tight then make fine adjustments from there. I have had my diff really tight, as in tight enough to destroy the red rubber O-ring that fits between the diff and adjustment collar. Even then it didnt make a noise like that!
The diff can also be loosened enough to allow the spur gear to turn without turning any wheels, but even then, no excessive noise.
On my Kyosho ball diff, I can see about 0.5 - 0.8mm of the red O-ring on my current setting.

If it persists, send it back for a swap out, but it could well be a gear meshing related issue and that should not be overlooked.

Keep us informed


2002.01.01, 07:16 PM
The recording was made with both wheels spinning.

I used a scrap of paper folded over so it was double thick to shim the motor. It is MuCH quieter now.

Basically, I went full loose on the diff and it still clicked (it runs smoothly but it seems like occasionally something gets stuck in the gear mesh and makes a clicking noise. I'm using the 6T pinion and the car has had about 5-6 hours of run time on it. It physically is in good shape still.

I have full bearings on the car and assembled the diff through the rear end with the included thin washers on the left and right bearing (the directions state it should be passanger's side) nothing is binding now.

The shimming is a HUGE improvement over what it was but it still seems to sound a little bad in the gearing.

I removed some excess grease and it now spins easier with the wheels alternating directions but still seems to get caught on some sort of bit of grease or something. I'm wondering if these are just high spots on the balls that will wear in over time?

I held one wheel and let it spin a bit to break in the balls a bit. I only did it for a minute or less, didn't make much difference though so I stopped.


2002.01.01, 08:13 PM
note: ball diff addons sometimes have a larger (or is it smaller?) diameter Spur gear... and may require a different combination of spacers for the pinions then the stock.

2002.01.01, 09:06 PM
Well I guess it's possible that Kyosho would sell spur gears that don't fit their pinion gears... wouldn't suprise me in the least.

I seem to have solved the problem with the paper shims but I would have to think that I shouldn't need to "adjust" things when I add Kyosho parts to a Kyosho car.

I'm still trying to figure out what seems like "sand" in the diff after I cleaned and greased everything thouroughly... it spins smoothly but catches every so often. It really doesn't catch much but I've handled ball diffs that have no such "sand" in them.


2002.01.02, 01:39 AM
The Kyosho ball-diff uses the same size (amount of teeth) spur gear as the standard diff.

Jeff, try placing the diff's spur gear under a magnifying glass of some sort, like the illuminated kind used in PC repair centres.
Examine the teeth on the spur gear, perhaps there it's a badly moulded gear or something like that.
As I said earlier, I (fortunately) haven't experienced any trouble with my indigo Kyosho ball-diff. Perhaps you got a duff unit?

I feel confident that if you highlight the problem to whoever supplied you the ball diff, they will gladly exchange it for you :D


2002.01.02, 09:24 AM
I will examine the spur gear tonight when I get off work. It seems quite a bit better than it was before but it's still a little noisier than I would like.


2002.01.02, 05:31 PM

Any luck on that suspicious ball-diff yet?
I still think it could be spur/pinion gear related.


2002.01.02, 09:39 PM
...... "First I had a problem with it clicking and sounding like it was going to come apart while it was moving but I believe that was due to my not having one of the washers in on the side that the wheel hub attaches to with an allen nut. Now it's still VERY noisy while it moves and I can't really get it to operate like my old diff (if I turn one wheel clockwise the other turns counterclockwise) it either is too tight or not tight enough and loud as all hell."...

hmm... isn't the thin washer supposed to be on the other side (the gear side) this helps prevent the thread going into your bearing or bushing in the motor mount... i'd suspect that you caught something in between the teeth of the gears, so inspect the pinion and spur gears (i once got a tiny piece of glass caught in mine and didn't see it right away, good thing i inspected the gears and cleaned it).... get an old toothbrush and brush the spaces in between the gears... and finally check the meshing of the gears... be sure that you using the right spacer/s for your pinion gear....

hope this helps :D

2002.01.02, 11:10 PM
Herman, I had actually put the washer on the spur gear side of the diff and the other side (which they instructions don't specify but I did anyhow). I verified I had shimmed the allen head hub side enough to allow free movement and added two pieces of 20lb paper to the motor mount to shim it a bit, it is the stock motor, mount, 6T pinion, and spacer (if there is a 6T spacer) and had the right mesh with the stock diff but the kyosho ball diff spur gear was too tight. The motor shims seemed to have taken care of it though, it's about the same loudness as the stock diff.


2002.01.03, 01:54 AM
hmmm.... well did you check the spaces in between the gears? make sure that there is no dirt in between the gears...

the correct spacer for the 6t pinion gear is the 1.5 square spacer in the plastic motor clamp (7 & 8 t use 1.0 rectangular and square spacers, while the 9t uses the 1.5 rectangular spacer)....

seems like you did everything right... the spur gear in the stock gear diff and ball diff is the same, if the gears are clean and the ball diff is properly greased, and gear meshshing is ok, i have no clue what could be wrong...

try changing pinion gears, and see if you have the same problem with that.... other than that, i wish i could've been of more help:confused: good luck

2002.01.03, 08:56 AM
Am I supposed to use the 1.5 spacer that came with the kit? My Mini Z is Japanese and I can't read the instructions :) I'm assuming it was shimmed properly from the factory because the entire rear end was preassembled and the ball diff instructions didn't mention anything.

Is the 1.5 spacer on the plastic tree a spare or should I seriously consider putting it on?


2002.01.03, 09:39 PM
if your car came factory assembled then you should'nt have anything to worry about... have you checked your spur and pinion gears?

fyi... here is the spacer guide for pinion gears...

the 6t pinion gear uses the 1.5 square spacer in the battery clip

the 7 & 8 t pinion gear uses the 1.0 rectange spacer (placed in between the motor and the motor well, you'll have to remove your motor first, to be able to do this) and the 1.0 square spacer in the battery clip

the 9t pinion gear uses the 1.5 rectangle spacer placed in between the motor and motor well...

hope this helps...:D if you do decide to change the pinion gears, make sure that you use the correct spacers.

2002.01.03, 11:28 PM
Doesn't the motor mount come with the correct shims in it from the factory? The only thing I would have changed by adding the ball diff is the spur gear. I've never taken the stock 6T pinion off yet. Everything looks great and it's finally quieted down but after adding a minute ammount of shim to the motor from some paper scraps.


2002.01.04, 03:39 AM
here's a copy of the manual on spacers... somebody scanned and placed in a different forum....


and here's the thread...


it's nice to hear that it is a bit less noisy... is your mini-z made in china or japan? just asking... if it's made in china, the motor mount might have slipped through quality control... but this will be probably the first time i've heard of it...

oh yeah you never did answer my question... whether or not you checked and cleaned the spur / pinion gears, keep them clean with an old toothbrush...:D

2002.01.04, 06:43 AM

Perhaps it's time to look into an alloy motor mount :D
It makes life a lot easier


2002.01.04, 08:43 AM
Herman: I have the 6T pinion and that pages says no spacer goes between the mount and the motor, I ended up having to add just a little bit of paper in that spot to push the motor out a fraction of an inch.

Mondo: I may, I'm trying to only buy direct replacements for parts as they break... I'm trying to get a full rear oil damper set and springs for the front and back next so I gotta live with my spacers :)


2002.01.06, 08:23 PM
master jeff....if you do intend to purchase an alloy motor mount, choose one wisely, some mounts don't work with the stock motor.

"Mondo: I may, I'm trying to only buy direct replacements for parts as they break... I'm trying to get a full rear oil damper set and springs for the front and back next so I gotta live with my spacers "

choose your damper set wisely too, some dampers (i.e. gpm) don't fit well with kyosho, so you end up buying their motor mount as well... however i was able to use a kyosho rear shock with a gpm alloy motor mount...

....in short choose wisely:D (hmm... how is it that i feel like i'm some kind of yoda or something?:D)

2002.01.06, 11:29 PM
I'm just going to buy the triple rear oil shock and throw my Kyosho center shock in my toolbox... seems to be easier.

Is the stock plastic h bar recomended for the triple oil shock or should I use one of my carbon ones? I bought really thick (1 mm I believe) h bars and have been sanding them down as needed... only did one so far and i went too far and it's VERY (.5 mm) thin.


2002.01.08, 05:03 AM
The Cf H-bars are too rigid to my taste, too bad I broke my original (that's why I bought the set anyway)I'll try sanding one down to .5mm and report back.
Don't have the fancy oil stuff though, only kyosho shocks. Mini-z how much is shipping to Finland? (I did e-mail you)


2002.01.08, 01:15 PM
Hi W-tone, sorry for the delay, I just replied to your email - thanks!