I would appreciate any ideas about a weird noise I get in my 81 300TD turbo(180K miles) at freeway speeds. It is a single note, always the same, and sounds exactly like the ringing sound you can make with a wine glass by wetting your finger and slowly circling the rim of the glass. It occurs at about 65mph and comes and goes, sometimes much louder. It seems like it might abate at faster speeds -- above 80mph. It will persist for the better part of an hour then go away. It is always exactly the same steady tone. It does not wow, howl or grind. I cannot locate it to the rear or front and the sound fills the car. I noticed it will sometimes halt momentarily if I tap the brakes. Also I noticed that it will sometimes be influenced by applying slight pressure to the steering wheel (i.e., while tracking straight, applying light pressure to one of the steering wheel stops within the sector of steering wheel play). I recently replaced the center drive shaft bearing etc, and recently had front brakes done. I have been having belt screeches lately but no reason to suspect a connection. The car's performance is great, and generally it is in very good condition. Any ideas would be greatly appreciated. I worry about a bearing but wonder also about power steering pump or turbo bearing. The odd thing is that the noise does not vary in pitch with speed changes so it does not appear related to RPM of anything. Thanks