What you describe sounds eerily similar to what I've experienced a few times. In my case once the cabin temperature warms up enough the screeching and needle bobbing stops.

The first time this occurred a few winters ago I removed the dash assembly and was able to recreate the sound by spinning up the Speedo with a drill. So my issue was not the cable. My fix was to apply some lube (I believe I used white lithium grease) to the gears inside the Speedo/Odo.

Fast forward to this winter and the wailing squirrel has returned on cold mornings only to disappear when the cabin warms. This AFTER I just installed a new speedometer cable. So, this weekend I plan on going back in and lubing the gears again.

Your noise may indeed be coming from your cable. I just wanted to share an experience where that was not the cause.

__________________
Joe

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1980 300SD - 495k miles - 'The Ambassador'
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Former Family Members
95 C280
73 280SEL
90 300D
87 300SDL (X2)
86 560SEL
84 300D
80 300SD