I just purchased my 2009 V6 4WD with 92k miles. I am in the same situation. Am in South Florida running from Hurricane Dorian and driving back to Phoenix. (Missed us thankfully.)The rear drive actually engages every time you start off. One diagnostic that's easy to run is disconnecting the connector from the 4WD ECU behind the glove box. Then driving down the road everything in the rear will still be turning but not under power. With the car on jack stands only the front wheels will turn. You may be able to make a judgement based on the changes in sound.
The local dealer said that my rear diff was gone and at $3800+ could be fixed.
I had them change the transfer belt $275+.
I would like to attempt to disconnect my 4WD ECU. If it stops the sound, is it safe to leave it disconnected for the 2000 miles I need to get home and get it properly diagnosed? Will it hurt anything? I will be doing highway. Please help as I will be moving on North soon.
Thank you in advance,