how do I convert my mechanical speedo to an electrical?

[Yellowbird RS]

I once read a thread of someone who did the conversion, using a 964's speedometer. I also know that one way or another I can attach the electric sensor to my gear box. My question is, what do I exactly need besides the above? Is it a plug in? or how do I attach it? Do I have to make any modification to the gear box? It is a 915 from a 1974 Carrera.

[MotoSook]

I bet someone would trade you a trans with electric pulse out for your 7:31 trans....

The mechanical drive on the early 915 and the electric drive look very different. You might have to get into the case and change the shaft...seems like a lot of work..but someone like John Walker would know for sure.

You could just cut the cable and adapt a pulser on the stubby end of the speedo cable inside the tunnel that would send a pulse to an electronic speedo that is available from a number of venders. Might even be able to make t work with a stock VDO speedo, if you could range the pulse factor.

Why would you wnat to change it?

[emcon5]

There is a hollow spot on the right side of the tranny case where the sensor goes, so it isn't an easy proposition.

What are you trying to do?

Tom

[Yellowbird RS]

my speedo is not working so I want to upgrade whit a 964 RS Cup that I found in a local shop this one is 320 kms.

[emcon5]

It would be cheaper and less of a PITA to send you broken one to North Hollywood Speedo or Palo Alto Speedometer to get repaired/refaced/recalibrated.

They can put any face on it you want, and your odometer will be correct.

Tom

[john walker's workshop]

pretty much takes a trans swap. there's a magnet ring on the side of the differential that works the sensor, that doesn't simply swap onto yours.