I have a 41 Olds hydramatic and the converter leaks back into the main transmission housing after it sits for a day or so. I know it leaks back because the dip stick is about 3" over the full mark. I have to wait about 4 or 5 seconds before the car will move. Does anyone know of a check valve that supposed to keep the converter full and if so where is it located.

 

I believe the check valve is in the fluid coupling. Look at the diagrams and you will see a spring loaded cup like thing. That is what I believe is the check valve. Perhaps it was installed backwards.