I'm not sure if this will be much use because I returned the car immediately with this issue instead of hoping it got fixed, but I had what sounds like the same issue. Rear drive unit was making a loud whine immediately when I drove it out of the lot. Essentially sounded like the motor was sitting in the back seat. I drove it a few miles and immediately returned to the service center.
I waited about an hour for someone to look at it because they were "extremely busy". They did (unofficially) agree the rear drive unit probably needed to be replaced. Next scheduled appointment was almost 2 weeks out, or I could leave it there and maybe they could look at it sooner. Once they officially diagnosed a drive unite replacement was necessary they would have to get special approval from Fremont and then have the unit shipped to the service center.
It sounds like you have the actual diagnosis now, so 1-2 weeks for the approval and shipping sounds likely. Then you are waiting on the service center to fit you in or now add you to the schedule at the back of the line which could be another couple weeks. The actual replacement doesn't take long, but the bs it takes to get to that point can be annoying.