my 94 xlt just decided today that at idle it would start surging, feels like the torque converter was catching on and off, but there is a loud howl from under the hood, but at idle the truck literally moves up and down its better in nuetral, but I can't tell if its the tranny reacting to the motor or the motor reacting from the tranny, I've read about the IAC, but I what I read sounded like rough idle or lope, not full on truck moving up and down...

I checked my trany fluid, looked ok, the truck runs up and down the highway fine, just basically the longer you sit at idle, the worse it gets, any ideas?

Check for a vaccum leak. Had a car today that was kind of stumbling on it face, and well - it was a vaccum leak. You could hear it with the hood closed. Anyway -- I would suspect a vaccum leak. Your transmission usually doesn't cause a rough idle.

-Drew