how to tell if/when power steering is going bad?

Here's the situation... starting back around June of this year I started noticing my steering was getting a bit stiffer, and not self-centering normally. It's progressively gotten worse to the point where I can rotate my steering wheel up to 90* left or right of center and it just stays there.

The pump and box make no noise though -- no squeeling or whining. I've checked the fluid level and it appears to be fine. No major leaks that I can see.

So would this be indicative of the pump going out, or the box itself??

:repair:

check to see what condition your steering shaft is in, also check the gearbox is bolted nice and tight. It sounds that either the gearbox is going or it is not bolted tight to the frame. Watch the box as someone truns the wheel back and fourth, if it moves tighten it..