Well, for my trans 4r70w, all that is required is a few drill bits (wire gauge), trans filter (might as well while you are there), two seperator plate gaskets, trans pan gasket if need. All you have to do is drill the seperator plate to proper spec, thus the reason for using wire gauge drill bits to get into the thousandths of an inch accuracy. Mark the selected wholes with the correct size of the bit, and drill. Replace with a softer spring in the 1-2 shift accumulator, and totally remove the 2-3 accumulator spring. Reassemble valve body to trans, and fill with fluid, test drive. The shifts become amazing, faster, firmer, and while cruising down the road, the shifts are not so firm, but only really noticable to the person driving the car everyday before and then after the j-mod. Just to give you an idea of how it works. And what I am asking is there such thing for the 4l60e? Not a shift kit that you go and buy from the store that you actually change springs in the valve body itself to raise pressures and shift firmness, but like stated above moves more volume faster, and by replacing the accumulator springs, firmer shifts without raising the pressures themselves and causing more problems down the road.