I had the same issue, I replaced the belt, still chirped. I replaced all the easy pulleys, chirp remained. One day I was messing around and squirted some water on the belt, the chirp went away...So figured it wasn't a bearing or anything, so I pulled the belt and used my drill with a wire wheel and cleaned all the pulleys really well, thinking there might be some type of liquid or something in the grooves. Chirp went away

So try that and see if it helps, spraying the belt with a bit of water and listening to see if the chirp goes away can help tell if it's the bearings or not. Good luck!

 

I have never bought a Gator belt but I have found the high quality belts much less likely to squeak, but if they do, I have sprayed AmorAll on the belt while running and usually after a few treatments the problem goes away. Works fairly well on the cheaper belts also but doesn't last for a long time normally. Been through 1 Suburban, two Jimmy's and an S-10 with this in the last 15 years.

 

My 89 S15 Jimmy belt squeaked for thousands of agravating miles. I tried lubricating the belt, replaced the belt tensionor, idler pulley checked the alignment of the power steering pulley and anything else I could think of to no avail. I finally tried the Goodyear Gatorback belt and that corrected my belt squeak. I became a believer. It has been quite a few thousand of miles with no belt squeak. My Jimmy has almost 450,000 and and is still my daily driver.

 

I finally fixed this problem on mine today!

A big Thank you to dryden3 and SuperG for the suggestions on adjusting the PS pulley. I pulled mine about 1/8 of an inch out.

I honestly couldn't think of why this would work because the noise seemed to be coming from the top idler pulley but it worked. No more noise!

I wish I had tried this before I replaced all three pulleys, the belt (twice) and rebuilt the alternator with new bearings.

I hope this post will someone else in the future.