Power steering Failure...

[Husker]

This afternoon I started my truck a loud whining noise shut off opened hood all looked good. Restarted same thing looked at pulleys all turning, whining coming from Power Steering pump. Had to get home so I drove a bit and steering hard to too turn but better at times, whining comes and goes. About half way home whining stops got a surge of power, belt broke. Anyway got home checked pump turned ok. Question is, Is it the pump or box?
350 in my 70 4x4 factory componets rebuilt pump a few years old and box was rebuilt installed about 2 months ago, no issues till this afternoon, Has fluid in pump and no leaks to speak of.
Thanks
Ron

[Daman]

I'm not sure but wanting to hear the answer.

I can drive all day in town and not have a sound then when I drive to work (highway 75 mph) I get a high pitched squeal. Changed pumps, belts and made sure pulleys were lined up. Small leak on the box and when I turn it off it slowly quiets down like it is relieving pressure. No other problems with steering

[hugger6933]

Both of these issues sound like the pressure regulator located behind the big nut where the pressure line screws into the pump

[Daman]

There's an adjustment? Or replacement. My pump is new

[Husker]

I changed the pump first did not help, changed box and pressure hose while I was at it. Bled the air out with tires off ground worked my great now. Before it failed it always squealed when turning now it does not. Not sure if pressure hose was kinked a bit not allowing full fluid pressure. New hose was cheap from NAPA I think it was $25.00 or less. I had just changed box out 3 months ago for leaks and I think the box was bad or going bad to only last 3 months. Anyhow working proper now.
Ron