1991 240 DL 4 dr 112K auto trans. My dilemna is as follows. While driving home friday, I noticed a high pitched whine at about 30-40 mph. This whine was quite pronounced and at first cut, sounded like a wheel bearing or a rotor squeal. On the way down to a stop, the noise whirs down to zero MPH. The noise follows rotation (wheel speed) not engine RPM. As I accelerated to 50 or above the noise changed to a steady "chirpier" squeal. Have you ever heard locusts in Texas in the summer? That's the noise. So far I have jacked the car and hand rotated the wheels and no noise. 2000 miles ago I changed the pinion seal on the rear diff. I fear it is a noise in the trans but i'm not sure yet. Any help?

Mark
90 740 GLE 16V, 87 740 GLE

I had simular noises after installing a driveshaft center bearing, it took about 100 miles or so to break-in. Maybe yours is going bad.
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Bruce S. near D.C.

Mark Whittier again.

since my last posting, I jacked the rear end and ran the vehicle in drive(safely) and noticed that after a few seconds as the trans shifted into 2nd the squeal I described before started. It seems to be coming from the trans, Any advice?

Mark

Put the trans in 1.

Wind it up to where it would have shifted into second and see if it starts again. You need to isolate whether or not it's a trans noise or a driveline noise. If the noise happens in 1st gear also, look to the center bearing on the driveshaft. That's the most likely cause of noise in the drivetrain, and is a weak spot in the driveline.

It's possible that the trans is making a racket, but that would be unlikely.

Also you can try to bring the RPMs up so that the trans shifts to 2 (with the lever in 2 or D). Wait until the whine starts, and then (don't try it if you're really speeding along, even on stands) drop it into 1 and see if it still does the same thing. Or let it shift to 3. Whatever will isolate the transmission from the driveshaft. The fact that it goes along with the road speed of the vehicle from speed to a stop means that it's obviously either related to the output shaft of the transmission or the driveshaft itself.
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Chris Herbst, near Chicago, IL. 93 940, 91 240, 90 240, 88 740, 87 240