I have an 83 300d and all of a sudden, JUST before 250,000 miles, it started making this bizarre noise. At first I thought something was rubbing on the tire but I've inspected them and that does not seem to be the case.

Here are the facts:

Unrelated to the engine and engine speed.
Unrelated to which gear the transmission is in.
Unrelated to whether or not I'm applying the brakes or steering.
Completely dependent upon my speed; the faster I go the faster the noise goes.
It kinda seems like the noise goes one full cycle when the tires go around at least a few times.
It seems to be coming from the rear of the car.


The noise itself is sort of a combination of the sound you get when you spin and electric motor when it is not powered and something rubbing and kinda squeaking. It's a pretty serious (sounding), very noticeable noise.

Also, and I haven't checked this out fully, but it seems like it makes noise more at slow speeds if you have just decelerated from a faster speed. That is, it's hard to notice at 5mph if you just got there from zero as opposed to having just slowed down from 60.

Any ideas? I'm pretty worried about this.