Squeal 1995 Dodge 2500 Van 5.2

I have a 1995 Dodge Van 2500 5.2 it has over a 100,000 miles on it. It is squealing so loud. We tried everything we can think of. We replaced the belt, idler pulley, tensioner pulley. Ran with no belt to check harmonic balancer and there was no squeak/squeal. We hook it up from the harmonic balancer to each pulley one at a time. And it does not make the squeal. Not until we put it all back to together. We also replace the alternator. Water pump. I had a mechanic stethoscope and listen and can not pin point? Please help.