Spoke with the dealer assistant service manager today to get clarification. Supposedly, the entire drive shaft needs to (eventually) be replaced since the bearings are going bad. The drive shaft is the only part that needs to be replaced, it is one unit, and the part cost is $963.
As noted above, the issue is heard - almost a grinding sound - right near 40 MPH when under a little bit of load. Originally, I thought it was a heat shield, but that is clearly not the issue.
I was able to record the sound the drive shaft makes under load, and you can hear it for yourself. The file is a small MP3
You'll be able to hear the grinding.
The assistant service manager mentioned it's more of an annoyance, that is not a critical "must" fix, but I'm concerned waiting may result in damage to whatever the bearings in the drive shaft roll against.
Is there another parts source available to procure the drive shaft at a lower cost? I'm seeing numbers under $400 online, but I have no idea what to order. I'd have a local shop install the shaft after I find it.
Thanks in advance for all comments.