If its the 4L30E , make sure you replace both O-rings in there.I went through this not too long ago where all the sudden I was spewing out tranny fluid and couldn't find the cause.It turns out the second O-ring was damaged and wasn't sealing properly.There is an inner and an outer O-ring , so make sure both are in good shape before you put them in , and make sure it goes in nice and straight , or you could damage one of them.

With mine , the only time it would spray out was at high speed , 50 MPH and above , then it would spray everywhere which made it hard to find the leak.At first I thought one of my hoses had come off , thats how much was there from the high pressure spray.