It sounds more like the pump than the converter. I would drop the pan, change the filter and do a full flush on the fluid asap. The longer you wait, the more crud will build up in the trans and fry other parts. Sometimes when the trans is "flushed" by those crappy machines it ends up clogging the filter. It might not be the solution, but it fixed issues that my customers (and myself) have had, and it's always a good idea to do a proper flush (engine on, pump out the bad fluid until it comes out clean). I'm sure there is a decent flush procedure here somewhere where you unhook the return line from the radiator.