91 Explorer pwr steering

I just bought the beast. Runs ok, but when it gets warmed up, the power steering makes much noise when turning either direction. Fluid is Ok, has a leak for sure, but not enough to cause that noise I think. Could it be the gear box, or is it the pwr steering unit?

I had the same problem with my 91 explorer. I cahnged the power steering unit and the sound went away. I don't know what the problem was but a friend told me it was a bearing in the pulley