Hi

On a recent week long trip to the Alps I noticed the steering on our 1978 Vette was whining/squeaking after much of the day spent  going up and down some of the more famous (and steep!) passes.  I checked the fluid once back home and it's up to the level.

Is it just the pump getting tired?  

Check belt tension. They also glaze up when getting old and worn. If the belt is setting to far down on the pulley,  it will bottom out, and not adhere to pulley sides. May need a new/wider one.