I have an Yukon 03 xl and have the same problem. I started noticing the noise when i had 17k miles. I have taken it to my dealership twice and they have not been able to help. I will be taking it to them once more and taking the technitian with me so that they can see what i am talking a about. Every time i tell them what is wrong, they look at me like if i have 3 eyes and they do not do anything. I notice the whining noise when my car goes above 15 mph. After that, i hear it every time i step on the gas. I even hear it when am going at 50 or 60. The other thing that i notice is that i also feel it in the steering wheel. Hard to explain. Will keep you posted.