Hopefully I don't owe the mechanic an apology. My wife got hit my two deer which hit the drivers side tire and went over the car. When I was taking the car to the shop I noticed humming increasing with speed and vibration. Took it home noticed it changed pitch and vibration was in park. Could perfectly create the same hum and vibration starting at 2k rpm and becoming quite bad at about 4K rpm again while in park. I checked for play everywhere , nothing. The mechanic said it's the front differential bearing and I said that doesn't make sense since it does it in park. I suspected engine or trans mount. You can visually see the upper intake manifold vibration with increased rpm. 2008 jeep commander.