Under Dash Rattle

[jgun]

I have a 2003 GMC 2500 HD Dmax/Ali and a problem. When I have the truck in drive and my foot on the break, I get a rattling noise under the dash somewhere. Sounds like it's on the driver's side and inside the cab, under the dash.

Any known problems in this area. It's almost 60 miles each way to the nearest GMC dealer and this is my only problem.

Thanks in advance for any ideas.