my transmission went out so I replaced it with a good transmission I had from another truck and bought a bd performance converter for it and it drives fine and shifts good but under accel and deccel it makes a rattling/ hissing kind of noise I think is coming from the converter. also when it is in overdrive and it is the converter is locked if I step on the gas it takes off fine but the O/D light starts flashing until I shut it off. any ideas? thanks
also I have IDP tunes on the truck

 

My idea would be to get the codes read so that you know what's wrong. Don't go to an auto parts store, they can't read Ford transmission codes.