[SRGN]

Given that it was good for a long time and the issue suddenly came up, I'm inclined to believe it's more than just a belt issue. I'd start with pulling the lines off the box, draining the fluid, and turning the wheels back and forth slowly from lock to lock(wheels off the ground) to get the old fluid out. I would try regular power steering fluid to refill after reinstalling the lines. PS fluid is a little easier to push than ATF given the difference in viscocity. I'm assuming that the issue is occurring at idle, make sure your idle speed is set to spec as well.