What could be the culprit? I do have a slow leak as the hoses and steering gear box are damp with fluid but no dripping or puddles yet. There no noise until I hit the extream left stop of the range and it doesn’t make any noise when dead ended to the right.

 

Fairly normal. I am actually surprised it doesn't do it in both directions. What you are hearing is the pump trying to turn the wheels even further.... valving in the steering box is controlled by how much torque there is on the steering wheel. If you are holding it at the lock, you are holding those valves open that want to help the steering turn some more. Since it can't, it makes interesting noises instead.