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I noticed the tensoner on the big serpintine belt seems to shutter I guess you could say or it has a slight vibration to it when you look at it closely when truck is at idle,its not completely smooth running.Does this mean its going bad or did i never notice it before and its normal?Cm 871 I replaced it once when it locked up.Luckily in parking lot of our warehouse .

I just put a new one on mine. It has just a little bit of bounce when it's running. I would say it's normal.

Mine has always been really bad. But I think part of my problem is that International uses too long of a serpentine belt.