What did I do wrong? FIXED IT!!

I am just putting this out there, how much trans fluid did you put back in? The converter holds quite a few quarts, although that wouldn't explain why it goes into reverse, but if the trans is pumping aerated fluid, or sucking air because of a low level, that may be an issue. The whistling may be the pump trying to pump air? either way, if you didn't dump 4 or more quarts back into it, Id check that out.