why the gearbox doesnt respond ? Or will rake longer time to response ?

hello ,my Hyundai atos gearbox start jerking !! there is a noticeable delay before the car move !! and i do change the oil ,clean inside also change the filter ,and sometimes it kicks or jumps like a horse !!!!!but gearbox doesnt have any noise !! i can be wrong but the gearbox has no noise ,so iam thinking the mechanical part or the gears might be ok !!!this auto geabox has some wires and connections...!! any help