Hello, my truck is a manual 2018 freightliner cascadia evolution with a DD15 engine. Recently, my truck started making a buzzing/humming-like noise when I’m accelerating at 45mph and beyond, and it gets louder the faster the truck is driven. However, when the accelerator is let off, the sound disappears. After doing some online search and whatnot, I thought it would be the turbo since it has never been changed and the truck is now at 573,000 miles. But when that was changed, the sound didn’t go away. The truck was pulling fine prior to the turbo change, and it still is now, but I thought it would’ve been that.
I have recorded and linked a video where you can hear the sound. It has only been making this sound and luckily nothing else has been affected(so far).
Any thoughts as to what the culprit would be?