I have a 99 3500. I have a high pitched noise that sounds like its comming from somewhere under the dash. It does it under acceleration and keeps making noise at a steady speed. Almost sounds like a loud vacuum leak. Never had this problem with any of my dodge's. Any Ideas?

 

It could very well be a vacuum leak. There are vacuum pumps for running the heat and a/c controls, possibly that is where your problem lies/

 

If it happens more noticeably during acceleration, then I'd be looking for a boost leak.
Intercooler boots are known to come loose, slip off, or develop little leaks that under pressure sound like a vacuum leak.


phox

 

I'm going to agree with Phox on this one...

But do you notice any smoke coming out your exhaust? (Most Likely black)

If it is a vacuum leak you should hear it all the time... But it possible to be a vacuum leak but un-likely...