Sorry if dupe but I couldn't find anything with the search.

I installed two new Gates alternator belts and they squeal like pigs. They seem to be tight on top but flopping a lot on the underside. Has dual belts, do I need both?

 

What year/engine?

I'm assuming 1992-1993 6.2L?

I have a serpentine belt which is just one big belt but that I believe was standard after 1994. If I recall its a matched set of 2 belts on 3rd and 4th groove...

 

1992 6.2

I'm wondering if these belts are a matched set. I never knew there was such a thing. They are the same part number.

 

They should have a little wobble in them. Too tight and your alternator life goes down. Keep playing with the tension and the squeal should go away.