3000 stall, firm shifts gone

Sounds about right for a loose converter. I used to chirp the tires at every shift with a 2500 conv. then i switched to a psycho 9 inch and a hotter motor in my 340 car and the firm shifts at low rpm's got real soft. Stand on the gas though and it was a totally different story. Stand on it and see what happens, if they are still soft it may be something else, but i'm willing to bet it is the converter.