Sounded like a hive of angry bees in the dash!
 

I was driving the '84 230CE yesterday and all of the sudden while driving a sound like a hive of angry bees started coming from the dash. It startled me since it was so damn loud. I couldn't even drown it out by turning up the radio. It was unbearable! The speedometer was working but it kind of looked like the needle was floating at speeds above 35. I haven't had a chance to pull the cluster. Is it the cable or is the speedometer dying?

That kinda sound is usually an electric/electronic relay short circuiting. On my '79 it happens when coffee gets spilled on the hazard light switch in center console.

If it was me, I'd pull the kick panel and make the cluster loose enough so you can pull it easily. Then the next time it happens pull over to side of the road and/or see if you can tell which relay is buzzing by feeling around behind the dash.

I'm more than sure that its related to the speedometer and or cable since it seems speed sensitive and increases in intensity with the increase in speed.

a speedo
 

cable going bad can make a hellof a racket.

and it will be intermittant at first. the needle will jump around too.

tom w

I'm hoping a shot of grease to the cable plus some WD40 to the back of the speedometer will help.

I found the problem! There was a tiny screw with a locknut on the inside of the speedometer flywheel which is on the opposite end of where the cable attaches to the head that was loose. I also put a small amount of grease on the gears. Bees are all gone. :)