I have had a whine for about 100,000kms/62,000miles now. It's most noticeable when things warm up and at 80-90km/50-55miles per hr with the a/c on.

It's coming from the front or transmission- pretty sure it's not the rear.
Thought I'd mention it in case it follows a similar pattern to yours..

__________________
1995 E300 Diesel