This just started a few days ago wen I was driving home I was doing 60 65 and the downshifted son could pick up speed around 2000rpm and started to hear a terrible squeal only does it on acceleration and not in park or neutral
anyone have any idea's I thought if it was a boost problem I would have the check engine light on but no light nothing truck has plenty of power just makes a god-awful squealing noise

 

Does it also do it on a downhill with a heavy load and the exhaust brake on? Mine does this too; it's an exhaust leak. One day I'll get around to fixing it...

 

Sounds to me like an exhaust leak or when my truck did this it was the actuator on the turbo . The actuator goes on them alot so thats why I switched to a 2nd gen setup then finally compounds . You can get an actuator and replace it for $3-400 or switch to a S300 series turbo . Here is an actuator if you need it https://www.dieselpowerproducts.com/...e-cummins.aspx