Power steering troubles at low RPMs

[GOTMINE]

At low rpms, my power steering does not work at all or at least very little . Unfortunately it's at low rpms when I need ps the most. When I have the LC in neutral and rev the engine, the ps comes to life.
I have checked the fliud level in the reservoir and it's where it should be. I also don't have any leaks from under the truck and the things look dry around the pump. The gear box is also free of any leaks. The ATF looks a little brown (maybe it's a little burnt). Would just flushing the system work or is my pump going bad? Do I need to rebuild it or is there another problem. I hope its not a valve in my gear box .

Any help will be appreciated.

 

[Tools R Us]

They came with tan hydraulic fluid, so maybe it's original? The gear that drives the pump is on the crank shaft held in place by the crank pulley bolt, if the bolt comes loose the gear can slip causing loss of assist.