Jeffreyt mentioned that his truck was squealing loudly when pushing hard while towing, and I've been chasing the same symptom for over a year. I'll let Jeff chime in to this thread and speak for himself, but here's how he described the problem initially:

My issue sounds the same. Only when towing, only when pushing hard, which means both boost and engine RPM are pretty high. Jeff thinks it's our turbos, and he might be right, but I'm not certain. I tested mine this morning, and it has no in-out or side-to-side play when moved by hand. I did see a "ring" around the turbine wheel when I looked at it this morning:



I thought, "that's it"! Except that I looked at a photo I took when I installed the ATS housing three years ago, and it looks the same:



I've got some other ideas, but need to run now. Your thoughts?

Mark

 

My other thought was the alternator could be making the racket. Last summer when this started, I took the belt off any my awful Ultima alternator from O'Reilly spun fine. When I moved the shaft up and down, it rotated on the front bearing. The rear bearing cap had fallen off, and the shaft was loose there. I thought a new alternator would fix the noise, but when I started towing again this spring, the noise was back

Someone else mentioned that it could be the belt. Mine only has 3y and 17K miles on it, but the tensioner is the original, with 12y and 136K. It still feels tight, but I'm not sure how to test it. I did replace the idler pulley, and that did not help.

Mark

 

Mine did it for the first time a few weeks ago towing a 25' ctr console on the TX coast. My buddy has a 97 SD and said his does it to from time to time. FWIW my turbo was completely rebuilt 20k miles ago. I need to replace my boots tho so hopefully thats it

 

Still trying to run this down... I took the belt off this morning, and checked the various pulleys. The cheap chinese alternator pulley is fine, but I noticed the power steering pump pulley has some in/out play. I've never checked it before, so I have no idea if that's normal. Do any of you?

Mark

 

Mine did it also when pulling a long grade. I came to found out it was the cooling fan locking up when it needed more air for cooling.

 

I have had this happen a few times too - It only happens when the cooling fan kicks in so I thought it might be the bearings in same. It happens so seldom I havent really looked checked the bearings. Is the locking up normal Jeff or is this from the bearings overheating ?

 

Funny you guys mention the fan thing. I just replaced my fan clutch, as it wasn't locking up. That doesn't mean it wasn't trying, though, and that may be the source of the squeal. I'll have to tow again to be sure, though.

Mark

 

I'd vote normal. I have changed a few SD p/s pumps and as I recall all of them had a little in/out play.

 

Thanks man! Most helpful!

Mark

 

Mark-Please let me know if yours is better while towing if you would. Also did your old fan clutch have any play in it? Also did you go oem on the clutch

 

Have you heard when the fan clutch engages before? It is a hell of a noise and usually only happens on very warm days when pulling. I wouldn't describe it as a squeel, more of a rush of air sound, but could this be what you are hearing?

 

When mine does it I hear the heavy air noise & then the squeal starts- It only happens (the squeal noise) when very hot ambient temps & pulling a long steep grade

 

mine does it occasionally only during the summer and when towing. I have narrowed it down to ( I believe) the intake boots on the spider.

 

Mine was doing this last year during the summer months. I went through it all checking everything. Ended up changing tensioner and belt. Problem gone. I can tell you I spent many of weeks not believing it was something so simple.

 

I've notice a squeal with my '02. Only its when its cold and is pretty random. It seems like it only will do it if i get on the loud pedal and get the rpm's up above 2k. As soon as it does it i back off the gas and it stops. Problem i got is i cant duplicate it all the time.