Well, most annoying is that our local suppliers with "American parts" sell a cheap chineese replacements. These rollers I've been replacing about a year ago, and made 5k kilometers on them. And the same problem popped up again. Nothing new.
Something broke in me, and I told myself to cut this never-ending story of fixing same problems over again. I've decided to keep up with original GM parts.

 

Funny story tho...
I've replaced the idlers and still the belt hit the high pitch.But this time only right after cranking.
For some time I couldn't figure it out. I only knew, that whenever I drop the belt, all is perfect. Then, when the belt is on, the sound comes on again. New A/C compressor, new alternator bearings, new Delco water pump, new Delco pulleys. I've even borrowed a stethoscope from my daughter toy set to find what that is. Not a chance.
Recently I got enlightened. My fittings of the oil cooler lines are sweating, so the drops of oil are forming down the hoses. On motion, they tend to fall on a balancer pulley. So the belt slips. And I am damn sure this is it. I could notice it with the battery voltage raising higher, while the squeak goes off.
I am posting it, as I find it not only a funny story, but it could be useful to someone.

 

I am experiencing that high pitched whine at the upper RPM range on both of my Blazers. I'm planning to purchase the one of the kits on Rockauto that includes the tensioner, idler, and belt combo. The choices are:
AC Delco
Dayco
Gates
Which of these would you all suggest? Of course I'm leaning towards the AC Delco kit, as they are all similarly priced. But Dayco is a reputable brand too. Not much experience with Gates however.
Thoughts?

 

From my experience I'd check for whining in a following order:
- alternator bearing
- belt wear (too loose)
- oily matter on the belt/pulleys
- idler and pulley
A stethoscope is a handy tool, if You're unable to say which one whines.
The brands You've mentioned are reputable and I guess they should be trouble free. I am running Delco and it is. The problem I've had was with the cheap replacements made in PRC. Not that it was of my choice, though....

 

I use a tire iron as a stethoscope. I grip the hex end in a fist and hold that against my ear, then touch the other end to the components. I’ve also used a big long screw driver in a pinch.

George

 

LOL Yeah, I remember an old movie, with a related scene (time 50m:42s):

(sorry, our forum doesn't seem to support a seek time parameter)

 

Holy crap that sounds dangerous.