Boxster 986 Drive train strange noise

[Wferrer]

Hello. I recently bought a pre-owned 2003 Boxster 2.7 5 speed with 15,000 miles on the odometer from an authorized Porsche dealer. After two weeks and only 120 miles of driving I noticed a strange noise coming from the left rear wheel. The noise begins at 20 mph and does not depend on engine speed, gear engaged or clutch. It is something between a high pitch whistle and the squeaking sound of metal against metal.
I got the car to the dealer and the diagnosed a faulty drive axle shaft.
Before that, I thought it might be a faulty wheel hub bearing or maybe the bearing that goes on the transmissión end of the axle.
Eventhough I accepted the dealer diagnostic and paid for the parts, the parts have not arrived yet after 45 days of waiting, so I'm planning to get my car out of the irresponsible dealer, get my money and do the repair myself.
Does anybody have had a problem with a noise like this one? I'm not sure if the diagnose is correct. I will be grateful for any ideas friends.
Thanks