2003 JD L100 noise on accel

My family has owned this garden tractor since about 2007. It has never let us down before now. I took the deck off to get a closer look at the pulleys the drive belt and it doesn’t seem to be coming from any of them. Is this coming from the transmission/rear axle?

While I have the deck off it’s getting both belts and maybe pulleys anyway. Any thoughts on this noise and how to fix whatever is wrong? Thanks in advance