High pitched, whistling from rear of truck.

[jwebinfo]

I have a 01 Chevy Tahoe (2 wheel drive.) There is a high-pitched, airy, whistling distinctly coming from the rear of the truck. I have very basic troubleshooting skills - thought it might be the fuel filter - that is nothing more than a scattershot. Any ideas?

 

My serp belt also appears to have some wear but I couldn't imagine it creating that noice all the way in the rear.

 

Thanks in advance.

 

Here's a link to a pic of the truck if needed: http://jweb-info.com/tahoe.html