[chasealley]

Tough to get a handle on this one without actually hearing it. 'Whistling' is tough. That usually makes me think blowing air, but of course can happen with sucking if the opening is the right size, usually very small. Larger opening would tend to make a slurping or sucking sound- that is if it was a vac hose that was completly off.

I have a bad idler bearing and it doesn't make a terrible sound. The races in there are plastic with metal balls. Poor quality but not likely to make noisy grinding on my 2001.

I've bought belts from crappy tire that were out-of round when measure with a micrometer and they tend to make some noise but not usually constant. When CT changed your alt did they change the belt?

And finally, my Ford factory alternator makes a horrible grinding sound that can be felt in everything connected to it. But keep in mind that CT usually gets factory second parts so there is a possibility you are dealing with a lousy alternator. It may even be something as simple as the new brushes in the alt.

But definitely get that scope. With a little experience that can help you pinpoint the sound.