I've been having belts self destruct since the dealer replaced a bad crank pulley. The first belt just shredded after driving out of the driveway and was able to make it back home. No chirping or warning. Replaced the belt and that next belt made it about 5k miles before starting to chirp. Checked the belt and the end was being worn off, causing the belt to narrow and stretch excessively. Replaced this belt that was about 5 months old and noticed the new belt was running about 1/8" off the end of the idler pulley - I have the GTTuning dual bearing idler. Belt is on all the other pulleys. About 2k miles before the crank pulley was replaced another shop replaced the tensioner and I lost the GTTuning tensioner pulley cause they didn't transfer it over. Also, have had a 17% Alta pulley for about 9 or 10 years and no belt problems. Tried loosening the screws on it and re-tightened but still is running off the idler.

 

Something isn't aligned properly, either the belt is improper length, crank pulley, idler, or SC pulley isn't bottomed out. Not many other reasons for the belt to walk off the belt drive.

 

So, just got around to trying to remove the belt tensioner and supercharger pulley, but it looks like there isn't enough room to get the tensioner out without removing the supercharger pulley first on the automatics. Also, the 10mm bolt on the bottom of the tensioner isn't there:



The 16mm bolt at the rear came right off with my fingers. Looks like the shop that changed out the tensioner left a screw off or didn't loctite and tighten them. Back half of the tensioner was barely still on.

 

Sounds like you need a new tensioner.
https://www.waymotorworks.com/superc...r-r52-r53.html

Also check that idler pulley as I've seen that aftermarket one you have go bad before.