I've been poking around these forums for a while. Up until now, I have managed to find the help I needed by reading old posts. Unfortinantly, I could not find anything related to this topic, so I am posting.

At speed, above sixty mph, in fifth gear, my car starts to hum and sing. The noise is practically identical to the sound produced when you blow across a glass bottle--wooooohhhhh--and it only occurs under load, when I press on the gas.

I should mention that I recently had work done on the car. The clutch failed, and was replaced by a well known, (mostly) trustworthy mechanic.

Any advice--preferably comforting, because I'm broke-- will be helpful. Thanks in advanced to anyone who responds.

Sunroof? Any type of windscreen, etc.? Turbo?

There car does not have turbo, and I have inspected all the windows (there is no sunroof) as possible sources of the noise. Also, since the noise comes only at certain speeds and when the car is under load, I don't think it is related to 'wind'.

Sounds like a problem with the driveline - support bearing, universal joint, driveline angle, etc.

Until you have the car on a lift its hard to track down the source of the noise.

How can I tell if it is one of the above? I am able to get under the car using jack stands. I did some time ago have the support bearing replaced. How do I adjust the 'driveline angle'?

With a rear wheel drive car the whole rear axle wants to rotate downward with load, lowering the rear portion of the drive line. The car has torque rod and trailing arm bushings to keep this from happening, which wear out.

Does your rear differentail leak? It could be low on fluid??? Hard to tell without inspection, I would take it back to the trustworthy mechanic.

I have a '85 240 dl...I had a similar issue, and it turned out to be low transmission fluid. Only when I went at highway speeds (60+). I changed out my rear transmission bushing and found the tailpiece (sic) of my transmission showed signs of abnormal wear.

Do you have any leaks (transmission)? It is easy to determine if it is the front or rear of the transmission based upon where you see fluid collect where the car is parked on a regular basis. Correcting them can be a bit of work.

Good Luck!

Breadman