The same thing happened to my buddy's 01 Cummins........turns out he was over boosting with the impeller getting hung up in the turbo.....did you check the impeller for side to side movement?...or hear it scrapeing the inside housing?...just a thaught i guess

 

you would know if the impeller was scraping it would sound like a supercharger and not a turbo

 

well my when my buddies went...u couldnt hear it down low, then heard it when the motor came around, but his still sounded like a turbo

 

I have blown 4 turbos and they all made different noises but it was all a whining noise but it could be anything. I would have to hear it firsthand to know for sure.

 

pul the intake tube off and start the truck, listen to it, rev it up a few times, look at it and listen to it