2005 Silverado K3500 8.1 Only about 80k miles on truck.

I have been to the Chevrolet Silverado 1999-2006 GMT800 Common Noises Diagnostic and did not find a solution.

I uploaded a video of the noise I am hearing while towing. The noise is only at the very beginning of video.
It is a very high pitch. It occurs when the vehicle is going uphill and working hard. You only hear it when video first starts. I am worried something is going to break while towing.

 

I couldn't hear it, but is it a squeal? What kind of noise would you call it.? Is it in front or back? I could hear something like a rumbling noise.

 

I hear it in the first 8 seconds of the vehicle. All other noise is engine working and the road noise.

I just found a video with a Chevy Malibu that has same noise

 

I agree that noise should not be there. I have heard carburetor motors make such a similar sound but you have fuel injection. I am going to see if I can find out what this noise is. It certainly isn't normal at all. I'd call it a whistling noise myself, BTW