Ok, so I have to replace the auto trans in my '84 300D and have to determine if the speedo is mechanical drive or electric... I know there's a typical speedo cable to the back of the speedo/instrument cluster.... Mechanical drive, right? I know, duh, but is an electrical unit actually just wires to the speedo?

Thanks all!

fred

I believe W126 is electronic and W123 is cable driven.

Mercedes used cables for years. My 1987 300D is cable driven (W124 body).

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Brian Toscano

Most electrical speedometers have a voltage generator at the transmission. One of the computer modules reads the voltage, and converts it to a different electrical signal that is sent to the speedometer.

Have a great day,

Thanks! Obviously a cable (mechanically) driven unit. F

If you have cruise, you will also see a sensor attached to the back of the speedometer.

Not always obvious. The W126 has an inductive speedo drive with wires running from the transmission to the speedo in a thich housing that looks just like a cable drive.

Sixto
91 300SE
87 300SDL
83 300SD