09 AWD Whining Noise
 

Hi. I have a 09 Limited with about 150k miles on it that has started making a whining noise in the front passenger area when I drive it. The whine gets louder as the vehicle speed increases, is not related to engine speed (idle has no sound or gear changes do not change sound volume), and is noticeably coming from near the shift lever area. This is my first and only AWD, so I am not sure where to start looking. On an old fashioned longitudinal-mount engine 4WD, I'd suspect the transfer case. Any troubleshooting suggestions would be appreciated. Thank you!