98 740il rear-end or axle?

Driving on freeway and hear noise that sounds like a card in bicycle spoke coming from rear-end or axle. Has done this for past 100 miles but today it made a loud bang and now sounds like a huey helicopter. Can it be driven to shop or should I tow on flat bed? Any thougths on what it could be and how much to fix?

There are a couple of possibilities and one of course is that your rear end (diferential) is bad, but moe likely is that the universal joint coupling is bad or the center shaft bearing is bad. Both are drive shaft speed related so the sound could be preceived as comminf from teh rear end of the car while driving. The symptoms are they start clicking and later knocking and finally bang! Sounds like you waited too long to get ti looked at, so there could be mroe things wrong with the drive line now that it has failed. If the defective components is lose, the it is not advisable to attempt to drive ti, get ti towed in and checked right away.

Hey Doc,
When you find out what the problem is, please share it with the board.
I'm hopeing you're a real doctor, you may have to holdback on some of those mp insurance payments to cover this one. Please take that in a nice way.
Good Luck