churping/squeeling in engine

i have a 2000 jimmy, ive heard a squicking/squeeling sound in engine for last week, so far ive replaced the idle pulley, belt tension pulley, alternator, and belt, but still it keeps up w/ the noise, i dont know whats goin on or even to figure out how to fix it, ne1 got any info on this?

Take a look at all the pullies, makes sure they are clean and properly aligned and not damaged in any way. Also, may sound dumb, but make sure the belt is properly installed, around all the pullies, in the proper groves.

One more thing to check while the belt is off. Make sure all the driven accessories, ie. alternator , power steering pump, water pump, etc. will turn easily. Something could be ready to seize.