Hey everyone I have a 1991 f150 4.9 and I bought a belt about a year ago for it. Well it still squeaked even after I bought the new one. But this last week one rib of the belt ripped off on the whole length of the belt. And ever since then it hasn't squeaked at all! So I'm thinking maybe a 6 groove belt is too wide? I think I might need a 5 groove of there is such a thing. What do you all think?

 

Your tensioner probably needs to be replaced.

 

It was replaced about 4 years ago or so and it even squeaked after that

 

did you replace the tensioner or just the tensioner pulley?

take some brake clean, then scuff pad all the pulleys, then brake clean again,

 

I replaced the tensioner and the pulley. I even have my old one and I put it back on after the new one and it still squeaked.

 

You might have a pulley out too far if it rubbed off the edge of the belt. Harmonic balancers can walk out a bit when the rubber is cracked. With the belt off check the pulleys by hand, spin and check for excessive end play.