I have never heard anything like this before. its a 2003 neon sxt. the noise started then a few days later the trany started slipping when the car is warmed up. I checked the fluid and its full no leaks or drips anywhere.i just need a direction to start in... thanks for any help...

 

nobody has heard this before???? bumpbump

 

Slipping and loss of power are signs that maybe your torque converter is going out. I was thinking maybe the bands need adjustment but that won't account for the noise.
Good luck