How tight should a ball diff be?

[Nobbi1977]

I am contemplating starting my DT-03 build soon. I put a ball diff in my DT-02 but even fully tight it did not feel like it was doing a lot.

How tight should a diff be and can things be done to adjust them more than just tightening the screw?

[kontemax]

It must be tight enough to don't slip.

When you assemble it, tight it a little bit and check, then tight again and check and so on, until it doesn't slip anymore.

Keep in mind that front ball diff is better a little bit more tighter than rear one. This will make a better balanced model.

Max

[Nobbi1977]

Out of the car should you be able to turn it by hand?

[speedy_w_beans]

Don't forget that ball diffs need to be broken in and readjusted, either on the bench or during the first run. The balls will start to seat in the rings, which loosens the tension somewhat and the diff then slips more. It has to be retightened to maintain its slip characteristics.

If you simply build the diff and then do hard full throttle accelerations on the first run, then it will likely slip, chatter or bark, and cause excessive wear right away. Drive the model gently and in some figure-8 patterns to exercise the diff, then check tension and slip again.

There's a sticky post on RCTech about how to properly build and break in ball diffs and slipper clutches; it's worth a read.

[ChrisRx718]

This is why running my TA03 was a pain - lots of screws to be undone before you can get the diff out! They were completely concealed though, which I guess helps with keeping the dirt out.

[Nobbi1977]

I might be better just putting some putty in the stock one and leaving it then, I did realise they required so much work. They are not easily accessible in the DT-02/3 gearbox.

[Backlash]

For a Team Associated ball diff, you tighten the screw until the spring bottoms out, and then back it off 1/8 to 1/4 of a turn, no more, no less...

Its a shame that other manufacturers couldn't make it that simple..

[super gripper]

you all are forgetting this is a DT02 ball diff - its a limited slip diff as you cannot fit a slipper clutch to a DT02/3

it's supposed to slip ..................

tungsten carbide diff balls are a good idea in this diff, never ever use ceramic balls in this diff !!

As the organiser of the DT02 Challenge held every year as shrccc in Surrey, it is a race event so the modified class is permitted the limited slip ball diff.

I have intimate knowledge of this ball diff and build them for other people, need any tips chap give me a buzz

[Nobbi1977]

I will look at getting tungsten carbide balls. I am just looking for an indication of "feel" and wether they should be built by the book, or paper slip, or if there is a trick or art to it.

[super gripper]

>>>Nobbi1977<<< PM me chap

[Nobbi1977]

Ok :-)

[oz-trash-cowboy]

Dorvacks' got the trick. Give the washes a flatting on an oil stone. Carbide balls and some ceramic grease.

[94eg!]

I set my rear diffs so they back tires don't make more than 1 full turn if I spin one with my open palm. Somewhere between 3/4 and 1 full turn is good. 3/4 is tight, and 1 turn is loose. It's going to take practice so don't expect to get it right the 1st time.

Also the diff WILL run in and loosen up so always re-check it after a run. Re-adjust it.

It's ideal to adjust the diff with it still in the gearbox. I'm not farmiliar with this type of diff, but they usually use a small hex screw in the center of one outdrive. To adjust, just pop off your upper link at one end on the side with the hex-head screw. Then pop out the driveshaft and stick your hex-key down the outdrive. Once you get it into the screw, you can make small 1/4 turn adjustments by turning the opposite wheel (instead of the hex-key).

Sanding the diff rings will make the diff much smoother, but there can be side-effects. Lots of times the diffs have a very loose feel when you initially assemble them. They may slip like mad, no matter how much you tighten them (causing some to ruin their diff screw by over tightening). Sanding rings usually requires a bench break-in before driving.

Break-in:

[94eg!]

Dorvacks' got the trick. Give the washes a flatting on an oil stone. Carbide balls and some ceramic grease.

Never ever use ceramic grease for the ball diff. It won't give the balls proper traction on the rings. You need silicone diff grease. I also use super sticky anti-wear grease (or associated black grease) in the thrust bearing.

[LongRat]

All ball diffs are by their very design limited slip diffs. But this absolutely does not mean the balls should slip or skid on the plates, ever. The limited slip function in an LSD refers to limiting the amount of slip of the unloaded tyre on the ground, and therefore transferring a defined portion of drive torque to the loaded wheel (with the most traction). It doesn't have anything to do with the slipping of balls on drive plates. You do that, and the balls will get damaged, and the rings will become scored. This leads to a gritty action and poorly defined preload. It is the setting of the preload, or spring tension, in the ball diff which dictates the amount of LSD action the diff has. If you torque the screw fully down, the LSD will not allow any differential motion of the two outdrives, and you get a solid axle. This could be referred to as a zero-slip diff. If the diff is too loose (but with no ball skidding), you get a loose action like an open gear diff where the unloaded wheel will just spin. This is a full-slip diff. The best combination is of course allowing a limited amount of slip, which gives you proper differential action for accurate cornering, but enough torque distribution to each driven wheel for stability and off-road traction. The absolute amount of spring preload or LSD action you require depends on the car, track and driving style, and it is a tuning aid for this reason.

[94eg!]

^On a car without a slipper, the ball diff will always give to some extent.....especially with race tires. As you mentioned, too much will damage things. This is why someone made the suggestion of carbide balls (prolongs the inevitable). They will withstand the slip much better.

Slippers were invented to protect the ball diff. Without one, slippage is unavoidable (with any decent amount of power).