I have a '80 Z28. I replaced the power steering pump because it was leaking around the shaft and I bled the system as recommended (lock to lock and no air bubbles) When I drive it the steering will randomly lock-up, maybe it will maybe it won't but when it does it's scary. Sort of like what you would experience if the engine quit, no power steering and you have to really get down on the wheel to turn it. I had none of these problems with the old leaky pump. I plan to replace the pump but I'm curious as to when you know the steering gear box is bad. Like i said earlier the whole system worked fine before.. just trying to understand what might be going on..