Brother of The benz, sgoodhart
All of us with VDO speedometers experience this failure.
The driven cross shaft disconnects from the drive shaft.
I've reassembled mine a number of times before giving up and taking it to a Service Center.
Don't do as I did, that is remove it myself.
Drive to the Service Center and let them remove the speedometer.
My cost was $99.00.
Happy Trails Beep Beep from The Spiderman in Houston!!!