Turbo problem?
 

I have a 2001 ram 3500 and I was towing my rock crawler on the interstate the other day,
not a heavy load I'd say 7000 lbs. max but when I would start up a grade and get in to it a little there was this squeling noise that sounded like it was right behind the glove box.Could the turbo be making this noise? I could back off the throttle a little and it would quit and seems to only do it in fifth gear above 2000 RPMs. This is my first experience with a cummins so any input would be appreciated.