1" Shorter Belt Squeaking on 06 w/underdrive pulley

First off just want to say that the underdrive pulley is amazing, and balanced far better than that stock heavy-weighter that keeps a door ajar...

So after the underdrive pulley install earlier this year, tried to get the belt to squeak with no success, but now that it is colder and hovering around freezing or lower for startup situations, for the first time the belt has started squeaking after startup. Disappears after full warm up.
I lubricated all the pulleys, burned the excess off the belt, and still squeaks from time to time.

So thinking 1" shorter belt works for warmer climate, but would a 2" shorter belt result in more tension for the colder/wet winter starts? Can't see why else this belt squeak is happening, unless one of the bearings is going like perhaps the alternator, but doesn't seem to be the case.

You can try a belt dressing spray (helps the belt not slip). I don't know if I'd go 2" shorter as it might not fit on. There is a lot of adjustment in the tensioner, I just can't be sure. Perhaps a 725k6 would work if the belt dressing doesn't work/last.

Been driving it this way just for the winter, now time to fix - took it to the shop and they said the tension was fine so thinking its actually one of the pulleys going/turning poorly. The squeaks happen more when the fan is on full, for ex. and when the signal light is on the squeaks are in time, so could this be indicative of the alternator bearing going? Still puts out 14.1 - 14.3 volts. Thought about the tensioner pulley too.

When I had my timing belt done, there was a bad speaking noise, took it back and they had to replace another pulley on the timing belt tract, I would say it is a pulley as well.

Ya, guess I won't know for sure until the alternator is replaced. Been reading posts theres lots on this here, and will work it into the next month.. have plans to do the plugs wires, and exhaust finally this spring too. Will post back when the alternator is done.

ya it was the idler pulley slowly seizing up.. surprised how long it took.. i knew its hard to get at that so i paid the local shop to replace the pulley and the tensioner aargh.. but its all ok still using the same 1" shorter belt that took all the squeaking wear

Thanks for posting how this turned out.