In the last 600 miles I have gone threw 4 gates belts truck is a stock 02 5.3 cleaned all pullies before installs checked for burrs can't find anything. When I installed last two there is a slight knock when cold coming from the front but goes away when warm. (this isn't the piston slap) I took the belt off and spun them by Hand and I hear no noises. The last two bets were shredded first forward ribs ripped off. The last one came off after I floored it and today I was pulling the boat up to speed and noticed I lost power steering it to shredded first two ribs also.
You guys know what I should look for first?

 

It's definitely a pulley somewhere. If it's ripping the belt I'd look at the balancer and the tensioner pulley as they're the only ones that are ribbed.

 

Where is the tensioner when belt is installed ? Can belt be longer than what you need? Also how about pulleys being alight.

 

Ps is ribbed as well Guess I get a small file tomorrow and do each pullie again I had the tensioner in mind but when you put a wrench on it feels tight. I have tried both 115amp and 145 I think it was just a little thicker which still ripped. Also to get the belt on you have to move the tensioner all the way till it almost stops then comes back maybe 1/4" once it's on. So possibly a burr somewhere and a worn out tensioner? Truck has 140k Used to see wot daily until it started doing this so I am afraid to gas it now haha

 

Is your AC belt Throwing off the main belt? I have the same issue with AC belt slinging off above 6600 rpm. Lowered shift points and solved problems.

 

Main belt

 

the 145amp belt is a tad longer

 

The two last ones that shredded were the 105s just checked all pullies all clean aligned and no burrs or sharp edges took tensioner off and sparyed with lube it's got plenty of tension. I am stumped

 

So main belt comes off but AC belt stays? Sorry not more help just going off what I went through.

 

Yes correct.
My buddy brought his truck over and I was revving it watching the tensioner his didn't move at and mine will kick 1/8-1/4?