Trans problems?

You should pull the pan and see if there is bits of converter in it.
It sounds like the converter exploded.
If it did, you will see small chunks of shiny metal.
If you do see that in the pan, the trans may be ok and just need cleaned out since the filter will keep most of it from going back into the trans.

Eventually it will build up enough small stuff to start sticking the valves in the valvebody and quit shifting.

Pull the pan, and take pics if you can, as a small amount of metalic deposits is normal.