Transmission issues

My transmission started having trouble shifting into gears. It would shift but there would be a slight delay. I added some fluid but I guess I added too much because then it would not shift at all. I emptied some of the fluid and got it to the required level. Now the car will shift into first hard second is fine but it will not shift into third. There is also a really loud whistling noise when the car is on. I have check to see if I can find any broke vacuum lines, but I do not see any.