I've been waiting for the whiring/whining sound to get worse, and it has, but I still can't isolate the cause. Thanks to the tips here: I have removed the idler pulley and its ok; I have felt the tensioner pulley it it feels and sounds ok; I've flushed and replaced the PS fluid and it hasn't made a difference nor does turning the wheels; the water pump seems ok; I removed the alternator and it checks out ok, and: the belt looks healthy. A stethoscope wasn't much help, although if I had to guess, I'd say the sound is the loudest on the drivers side.
So, I sure would appreciate hearing your ideas - I suspect the front A/C bearing but dread the cost and complexity of repair. Pretty hard to tell here in winter, but think the sound is actually quieter when teh AC is on. Does anyone have any experience changing the bearing while the unit remains in the truck?
Thank you.