grinding problem

[DreamSpeedPerf.]

ok so i was stuck in this wonderful miami traffic and i start hearing a hissing sound coming from my tranny area..then it started getting a little louder but would go away when it shifted to second. so i thought i would go home and check it..but as i started getting closer to my house it started getting worst to the point where it wasnt shifting and when i would stop and start moving its was grinding mad crazy. so when i got home and put it in park all you hear is metal grinding so i think it might be the converter..so i let it sit for a minute. and went outside,started her up and its like nothing ever happened. mind you that thing sounded like wwii was going off in my pan..please help me out hear im completely lost..i just put the tranny in like two weeks ago after blowing my last one