Did any one stop to think about rotational mass, on road cars wheather they be 1/8 or 1/10 have tires and wheels that are no were near the wieght of a buggy wheel and tire comb and if you add into the eqausion truggy wheel and tire combo's there is no way a ball diff that could handle the power that we apply to the wheels of our off road cars would be feisable for our cars.
1. The size and wieght of the tungsten or steel balls that would need too be used make these diffs would make the cars much heavier then our current kits and add a ton of drag on our drive lines increasing center drive shaft wear and decreasing fuel mileage
2. Center of gravity, this part would have to be large and bulky, so along with adding wieght to our cars we are moving the wieght higher up on the chassis and on top of this think about the increase in size of our gear boxes your going to add a ton of weight.
3. The mear size of the part wouldnt allow for correct gear ratios you wouldnt be able to design a pinion that small to allow for correct gear ratio's and still have a reliable drive line.