Unknown squeal

[AMink]

When towing, I get a squeal (like a high pitched, angry cicada?) when the truck downshifts and the rpm's go up. Sometimes it stops fairly quickly, other times it keeps up until the truck upshifts again. Then it stops cold. I sounds like it's coming from the driver's side but I can't be sure. This does not happen when not towing, even under full throttle, downshift, up a hill. Could this be the fan clutch? Or perhaps the Jake brake vacuum pump? The first time it happened was pulling up the mountain going into Jackson Hole from Driggs.

 

[JBallou]

I would be willing to bet that it is the serpentine belt. Only use a new Mopar belt. The service interval is quite short, something like 22k. I had a similar issue and that's exactly what it ended up being.

The fan clutch engages slowly and the sequel increases die to belt slipping. Only could get to happen under load when towing.

 

[Mathes308]

I had the exact same sound, then one day it started doing it off and on at an idle.
Crawled all over, hard to hear over the clacking engine.
Just for giggles I stepped down on my exhaust tip, cicada sound went away. Still haven't found it, but now I'm sure it's the exhaust rubbing somewhere, every time it comes back kicking the tail pipe quiets it for a while.

 

[AMink]

I checked the clamps on the intercooler boots and all needed snugging up. I'm hoping it's as simple as that. I'll be towing again next week, up some good grinds, so will know then. Also found that the rubber hoses for the Jake brake were all getting cracked around the ends so I trimmed them and reconnected. My Jake wasn't working as well as it did so I'm hoping that's the fix for that too. If the noise still goes on I'll put on a new belt, though the belt is pretty new.

 

[TRAMPLINEMAN]

I hope your quick fixes solve your problem. If not, it could be the belt as mentioned above, anything's possible. I'm just having a hard time with the 22K mile change interval. My last four Cummins powered trucks had a combined mileage of around 700K miles. Out of that, I changed one belt due to a seized pulley that frayed the belt.

 

[Mathes308]

Same here, I don't change belts until they become a problem or shred.
Not the best idea but 22k seems early, maybe every 50k

 

[BigPapa]

My belt has over 250K on it..........

 

[JBallou]

I'm just going off what I remember seeing in the owners manual. I know it sounds super short to me cause nobody ever follows anything other than the oil change interval. I will look again. Give me a bit.