I've got a 1988 GM power steering pump connected to a 1995 Chrysler rack & pinion unit, it all works very well except for the pump is whining a little.

I've tried jacking it up and running the engine at idle while turning the wheel slowly left-right multiple times. I've also hooked a vacuum pump to the PS pump while turning the wheel left to right. The lines are new as is the pump and rack, I had the same problem with a used pump and rack. There is no foam in the fluid and I rarely get any bubbles during bleeding. I'm certain there are no leaks or any way for air to get in the system. The whining is not too bad, not like some I've heard.

It's not the belt, there's a big difference between the sound of a squealing belt and a whining pump!

What am I missing here, should I adapt the proper Chrysler pump to my SBC, would this solve my problem?