If just changing fluid approx 4 but if putting rebuilt approx 10 to 12 quarts.After you add 3 if just changing then start up and with foot on brake put in forward and then reverse and then forward then reverse now park and check dipstick to see if between lines .If you need more add the next quart slow as to not over fill.If still not between lines do the forward back thing again and the recheck.A little over is ok but you don,t wont to be to much over.