Power steering squealing

If belt is slipping you would have intermittent in and out of the power steering and if the pump itself is going bad you would normally have a loud constant squeal along with hard steering and possible loss of PS fluid.

Any time you are getting noises like this it is normally one of two things. First there is air in the system and the other is the pump is failing. The noise is the pump aerating the the oil which causes it to pressurize air rather then oil and that causes it to squeal. Or there is a just a leak or no fluid and so it is pressurizing air.

Here are some guides that will help with this if you need to flush the fluid to start with but since it gets easier when you speed up, that tells us that the pump is weak and probably leaking internally so it is bleeding off the pressure.

https://www.2carpros.com/articles/power-steering-fluid-flush

https://www.2carpros.com/articles/how-to-replace-a-power-steering-pump

Most likely you need to replace it but if you would like to rebuild it, please see below for the detail on how to rebuild it.

Let us know what you find. Thanks