I'd say it's almost impossible to never turn the steering wheel all the way. I know Subaru says that, but I say it's completely ridiculous. I've done it 100s of times, sometimes even while on the throttle HARD, and my rack and pump are just fine at 60K.You should never, ever turn the steering wheel completely to either left or right. It puts excess pressure and stress on the power steering system and rack and will cause damage. The sound you hear is the higher-than-normal pressure in the pump and rack.