Volvo truck making a wooing noise

So my truck is a 2018 Volvo Vnl 670 with a d13 engine in it and sometimes while driving and especially while idling I hear a what I guess you would call a wooing noise. The volume of it changes and it happens randomly I don’t know what the issue is. Sometimes it is a little woo and sometimes it is a little longer woo.

 

so, its like

woooo! WOOOOOOOOOOOOOO?

 

Like this?

 

Whoo... I am stumped.

 

Sounds like a hog calling contest in Arkansas. He he he.

 

That's the new Curly option, or the Rick Flair Edition.

 

Air moving past the mirrors

 

Do you need glasses and them American best eye glasses have your order and that owl is following you around.

 

How many miles? I hope not but... could be the idler gear , it's been defective by design in Volvo D13/11/Mack mp 7/8 , they had a recall/pinning but your truck is very new and understand was upgraded. Still, i read about D13 with 200-300k miles having this isue. My D13 /2010 idler failed 3 weeks ago, making same noise you describe at 1,1 million miles , idler gear failure is like engine failure, i was quoted 18,000cad dollars for gear repair/replacement only( 200$ part only, but lots of labor, is located in the rear of the motor, hard to access it, have to remove transmission, gear cover) . I chose to install a new/reman motor , still im shop, i'll be done next week. I did run 1,833, 000 miles on my last truck 2008/D13 and didn't have this problem. Check it, if is the idler, don't drive it , once the gear gets loose on shaft and starts rubbing against block/gears housing could contaminate the oil with metal shavings, destroy the motor.