That sounds logical to me. I can check that without waiting for the noise to return, too.

If it's the alternator I can totally ignore it until it fails to produce electricity...right? Granted, that day will suck.

well typically when the alt fails especially bearing wise it locks it up thus dystroying the belt.

if it comes and goes id say you have some time left but id be weary of driving it super far from home

Running an alternator till it fails to produce electricity is usually a voltage regulator failure. Voltage regulators generally don't make any perceptable sound, but if you have problems your voltage will fluctuate, and one day it just won't work.

Hmm...if it locks up, that's not so great.

Perhaps I'll just wait until next month and see if I can scrape up the money for a new alternator by then, assuming that I positively diagnose it as the alternator.

Check it and if it is the bearing just change the bearing. They should be standard sealed bearings.

I didn't know alternators were that easily serviceable. Cool.

Yes, alternators are serviceable, and you can get bearings and even new voltage regulators for them, but if all you want is a stock alternator you can usually get a rebuilt stock GM alternator with a lifetime warranty for $50. I did splurge when I put a new alternator in The Beast - When the original alternator gave out I put an upgraded 165 amp alternator in. The Buick and Rusty are both running 105 amp alternators when they came stock with 70 amp alternators. I always believe in oversizing the alternator.

Where could I get a rebuilt unit for $50?

Mine is already an upgraded capacity unit for my towing package, and it's way more than I ever need even when using four electric brakes heavily on my camper...

When an alternator bearing fails, it can be rather spectacular...been there, done that.

If you're running an oversized alternator you won't get a $50 one. The last alternators I bought were oversized, but still stock alternators in my Buick and in my 86 Chevy. I think those ran me like $70/ea and came with a lifetime warranty. I think I bought them at the local NAPA dealer. I could have had the original 70 amp alternator for about $50. The alternator in my 98 GMC is a custom aftermarket alternator, 165 amp. If I remember correctly stock is 120 amp. I oversized the alternator because its nice to be able to jump start anything, and I was thinking about installing an AC inverter on the truck at the time.