I recently started hearing a squeeking noise coming from my engine when I first start it up in the morning and goes away some what for a few minutes then it will randomly get louder while driving on highway at 2500 rpm. Noise get faster beat to it with the more rpms. And yes I took both of my belts off and still has the noise. It's a 2001 gmc 6.0 HO. Thanks Jeff.

 

Thanks for the input guys.....

 

It could be also caused by worn out alternator bearings.