[fennacf]

If you have an early 85 you'll lose your speedometer with the conversion. You can use a late model 944 transmission and early 911 electronic speedometer in the older 944 instrumentation clusters.

I had to convert to the electronic speedo when converting to brembos.

I have an 84 chassis with an 88 transaxle and an 84 911 speedometer wired to the sensor in the transaxle.

Here are some of the details if you decide to go electric (I also have PowerPoint schematics that I can provide):

The speed sensor used by the 944 is a Hall Effect Sensor with differential amplifier so it needs a power source where the 911 does not. Here are a few details for the wiring.

Wiring connections are as follows:

Connected Pins "A" & "+" from the speedo and lead "H+" from the sensor to 12V ON/ACC power. Connected pin 31b from the speedo to "HG2" from the sensor. Connected pin "-" from the speedo and Pin "3" from the sensor both to ground.

Sensor differences:

From the schematics is appears that both sensors are impulse sensors but the 911 uses a magnetic type sensor while the 85.5+ 944's use a Hall Effect Sensor. Both produce a sinusoidal output and for this application were interchangeable.