L90D Tranamissoin low oil and power

So my L90D gradually leaks oil from the top of the transmission into the drop box. It doesn't leak any oil to the ground.
the oil gets lower on the high side dip stick and the drop box is overflowing with oil. so logically i have just been keeping an eye on it and adjusting the levels week by week. obviously the tranny slips when you let it go too long. I'm guessing thats the converter?

Any thoughts on whats wrong and how to fix this issue because as my solution works my guys aren't the...

L90D Tranamissoin low oil and power

L90D Tranamissoin low oil and power