I have a 2500HD 4x4 and since new it has had a loud hum/moan sound at 1700-1800 rpm. It does it in all gears and neutral. In 5th gear it is running 55-60 mph which is were I have to do alot of my driving. Please tell me there is a fix for this because I like the truck alot, but the noise drives me crazy. Its been to the dealer twice now. Any info would be a help.
Thanks

Trying to diag a noise over the internet might be a little tough. I personally have not had any with a complaint like that.

Make sure the down-pipe heat shield bolts are not contacting the firewall heat shield.

I had a gasser, the exhaust hanger that is welded to the pipe was contacting the exhaust hanger bracket by the transmission.