Idle Noise 4.3L GL

I’m having a squealing noise when I move from drive to idle.
The noise is not there on start up. I can get it to go away by restarting the engine. The voltage drops as well and my fish finder kicks off. I have tightened the alt belt. It does squeal when I start. The sound that concerns me sounds more like a pulley or bearing than a belt. Any ideas? Mainly concerned that I’m damaging my transmission.

remove the drive belt and spin each pulley, one may be worn , listen to the sounds they make, the idler pulley(stationary and not conected to ny accessory) is known for making a metal to metal rubbing sound, also the tensioner pulley will do this as well.
then there is the stethoscope method, take a long pipe, metal or pvc, and touch the bolt on the idler pulleywith 1 end and put the other end to your ear and listen for noise, do the same with the tensioner pulley, you can also move it to the alternator body, p/s pump and waterpump (not the pulleys themselves, just the bodies) and listen for the sound, you'll find it for sure.