Is this on your 2013? This is a super long shot, but the LML's had problems with the rubber fan stator isolators flipping forward and rubbing a pinhole in the radiator, which definitely has cause squealing noises due to coolant contamination on the belt. However it sometimes is very hard to notice.
Coolant contamination makes belts squeal drastically btw.
So, I have found out recently that the Dayco Belts have a tendency to squeal while still fairly new. I just bought an AC Delco to change out tonight. Same things, idler and tensioner pulleys are new and the belt is relatively new. Sprayed water between belt and alternator pulley and squeal went away. if this doesn't work, going to gator back belt.
I have had some luck with your regular ol WD40 on the belt. Since WD40 sucks for anything long term because it drys up and leaves a sticky film. It is purfict for belts. Also seems to soften the rubber a tad too which also helps keep it from squeaking
Anyone know of a good belt in the 149" range that won't come apart from RPM? Or one to use with a van thermostat housing and dual cp3's...Our truck during the UCC lost 6 belts. We have been using Gates belts. All brand new idlers and a brand new metal wheel tensioner. We even tried a plastic wheel tensioner. Same results...if we saw 4600+ rpm, it was guaranteed to have shredded the belt. We tried different cp3 brackets and even a new cp3 pulley.
The belt would either snap right in half or it would shred. I've been running the exact same belts and routing on my personal truck with zero issues. I have never seen over 4500 rpm though, so I am assuming the rpm is what is killing them.
I've got the gates 149" and have seen 5k when my old trans was slipping. AC Delco tensioner, AC idler, PPE idker by the dual pump, and PPE idler down by the crank/tensioner area.
Recently tapped off power steering resivoir low pressure return and added a cooler, along with sucking out as much fluid as I could. Old fluid smelt burnt and looked brown.
Sequel turning left from a stop is pretty much eliminated.