Ball diff setup?

[racegypt]

OK I will keep this simple in the hope of an answer.

I am rebuilding an Egress with ball diffs. The diffs were very siff and felt nothing like the ball diffs I am used to. After opening, inspecting, cleaning and lubricating - they still feel lousy. There are no signs of wear as the car has run very little. What is going on? What did I do wrong? I can't find ball diff instructions on the web, where should I look?

Please help.

[WillyChang]

Are they 'stiff' or are they 'gritty'??

Stiffness is adjustable... just loosen the screw.

Gritty means the balls have flatspots and should be renewed.

Egress diff shouldn't be overly stiff; maybe slightly stiffer than

a touring car due to the larger/offroad tyres. But the stiffness is

entirely adjustable on a balldiff.

[DJTheo]

Larger tyres would make it feel less stiff as you have a bigger torque arm (radius).

Cheers

[jozza]

What difference does the stiffness of the ball diff make to handling? I've had a look in my touring car setup guide and can't find any mention of them, would be interested to know.

[sosidge]

A stiffer diff could increase traction on slippery tracks.

But it will also add drag in cornering.

[sosidge]

Oh, and the older Tamiya ball diffs are rubbish, with the silly spring washer system. Try taking out one of the washers to get a looser diff, but it may start slipping.

[racegypt]

Thanks guys.

The diffs don't feel gritty, but when you rotate one outdrive and hold the gear it is very stiff. I compare this to the feel of HPI or Associated ball diffs and there is no comparison. The HPI and Assoc diffs are very smooth even when adjusted to give very little diff action.

The diffs don't have any adjustment screw, they just bolt up with three screws. Tension is by internal cup washers and appears not to be adjustable. I have found shims in the inside. I guess I should try removing a shim to see if that helps.

[SJoerD]

Just wondering, but are the diffs well lubricated? I think they are begging for some Tamiya ball diff grease the way I hear it. []

After that, maybe you can loosen the screws of the casing a bit and see if that helps? [:0]

[mud4fun]

I've tried running ball diffs in buggies before but on a severe off road course they are a waste of time, gain more by stuffing a normal diff with plasticine and oil (sounds daft but it works) which forms a limited slip diff. Believe me the traction that you get from a locked back end compared to an open diff is vast, not recommended for hard or flat tracks but definitely for off roading or bashing about in the woods etc go for locked instead. I also tightened the ball diff right up on my old FF01 based mini which I used on our track, far better traction than running it loose. However, locked back ends or tight ball diffs give poorer turning circle so a tight twisty circuit becomes 'interesting', fortuneatly locked rear ends slide out better so you can have fun sliding your way around each bend....[]

[racegypt]

The diffs are well lubed with the same grease I use in my other manufacturer's diffs. I am rebuilding the vehicle to run on a tight asphalt track with wooden jumps, so I think that the diff's are important. (Anyway I have no alternative diffs to install). I just wanted to hear from other Avante/Vanquish or Egress owners with old style ball diffs if they had any tips. The large balls in the center had been well lubed, but the smaller thrust bearings were less well lubed. It may be that they are flat spotted and need to be replaced, but there are no clear score/wear rings on the face of the thrust washers. Maybe I am being too picky!

I still wish that I could find the original Tamiya assembly instructions. The Egress manual on this site seems to start at page 20, which is when the build is almost over!

[DJTheo]

quote:The diffs don't feel gritty, but when you rotate one outdrive and hold the gear it is very stiff.

id="quote">id="quote">

Those old ball diffs are and should be hard to rotate from the outdrive as otherwise they would slip (also don't untighten the screws as the same might happen), but rotating from the wheel shouldnt be very hard.

Cheers

[mud4fun]

Sorry racegypt, didn't know you were running on tarmac. I have raced with other people running egress etc before but only on rough grass/dirt tracks and they used to run the diff very tight or lock the back entirely but as you say tarmac requires the diff running free. Cheers, Ian.

[WillyChang]

[racegypt]

Thanks WillyChang,

Apart from getting the spring washers upside down, I seem to have assembled them correctly. I tried rubbing the thrust washers on fine emery paper and that has helped. I think there may have been some tiny rust particles. The washers were dark color, but looked smooth to the naked eye. I will assemble the rest of the truck and test it.

Any idea why the first 19 pages of this manual are missing on this site?

[Toykid]

As with all ball diffs, how much pressure, ie how much you tighen the screw/screws greatly affects the diffs feel and performance. The problem with the egress diff is the pressure is applied across 3 screws. What were they thinking? If the pressure is not equal on each screw the diff will not feel or work correctly.

The standard setting for a ball diff is to just tighten the diff enough so that when you lock both our drives you can not turn the center gear. A little tighter and the diff will start to feel gritty, a little loser and the diff will slip too much. Once assembled give the car a run before checking the diff again. Normaly a diff will feel smoother after its first run.

Hope this helps,

James.

[WillyChang]

James:- pls reread the instructions page closely.

The 3 screws that hold the 2 halves together must be "fully screw in".

then at the bottom last inch..

"Differential can be adjusted by using more or less spacers (SD3)" [8D]