Speedometer signal ph1...?

[Falk]

Hi,

A friend of min has put a gearbox with a plate or torsen diff (don't know which type) into his ph1 172. (I haven't driven the car but he says it works great, really impressive traction. I wan't one too...)
Problem is the new diff has no speedo drive possibilities.
I had a quick look at the wiring diagram of my ph2. On my car it seems as the speedo gets its signal from the ABS unit, appearently not on ph1 as there is a sensor in the gearbox.

Has anyone had the same problem and found a solution? Is there an easy fix to make the speedo work on a ph1 picking the signal from the ABS...?
Is the setup/wiring of the dash/speedo totally different ph1 vs. ph2? I understand ph2 has some kind of multiplexed bus driving the dash... correct? What about ph1?

I haven't seen the sensor from the box, but I guess it's a simple inductive type. One way to go would be to put a trigger wheel on the right driveshaft.
Another way would be to use a 'blackbox' converting the signal from an ABS sensor to work with the ph1 speedo.

How many pulses/rev will the ph1 gearbox give? How many pulses from an ABS sensor?

All ideas, good or bad, would be appreciated...

 

[16v_jon]

If you have the below connector in your fuse box the yellow wire can be used to feed the speedo wire on the gearbox connector which is also yellow

 

[Falk]

Thanks!
Is it really that easy...?
Just joining the yellow wires together. No other connections neccesary?
My ph2 have the connector in the fusebox, I'll have to check if there is one in his car.
Why do ph1's have a speedo sensor in the gearbox if you can pick the 'ABS'-signal from this yellow wire?
What about later cups without ABS, do they also have a gearbox sensor, as this ph1?

 

[Falk]

Just received a message from my friend working on his gearbox swap / speedo signal problem.
The yellow wire pictured above seems to give no speed signal, just a steady 12V when ignition is turned on....

Any other suggestions?