Electronic Speedometer

[niall]

I have a 3.0L 1975 carrera.

The PO put an electronic speedometer in the dash, this does not work as I suspect the original was mechanical.

If this is the case can the electronic gauge be enabled to work?

[Dennis Kalma]

The electric speedometer works off of a disc on the ring gear assembly which has 8 magnets on it. On the outside of the case is a little dimple which holds a sensor which turns the motion of the magnet into a pulse, 8 per revolution, which in turn makes the speedometer go.

I have an electric speedo in my '75 911S, I was able to put it in when I replaced the transmission. I used a later transmission housing with the dimple in it, fitted the disc and away we went.

While any 8 pulse signal would do the job (you could attach magnets to the axles or wheel hubs, pickup on a stationary local point), I suspect the easier answer is to just get a mechanical speedometer..

Dennis

[RoninLB]

1974-75 mechanical 91164150229