W123 Mechanical Speedo to Electronic
 

I'd like to convert my 1980 280TE 4 spd manual trans with Mechanical Speedo over to a Getrag 717.402 5 Spd manual from an 84 280SL with a electronic cable output. I have the electronic speedo from the 280SL. Should I just need the original speedo to trans wiring from the 280SL, or is their more components needed? It also might be easier if I obtained an instrument cluster from one the years that the W123 cars had a electronic speedo, then trying to adapt the 107 electronic speedo into my existing cluster.
Can anyone be of further help?

I would be really curious to know if a W123 has ever, ever been equipped with adigital speedo...

Try starting with 1981 300TD for digital Speedo W123 useage

Mech. Speedo to Electronic Speedo
 

Job complete. Used mid 80's Euro 123 speedo, 3 wires to hook up between existing harness & Speedo Trans Hall Effect Pickup

Wiring Conversion for W123 to Electronic Speedo
 

Hi,
I obtained a partial wiring harness from a W126 car. From the Trans Speedo Sensor the White Wire is G+ & the Brown wire is a ground & both attach to the Electronic Speedo. There is a Black wire coming off the Speedo Plug, as well. This is your 12 Volt source & should only be powered up when car is on. These are the only wires I needed to use to make speedo work. The needle reads dead steady, as compared to cable speedo's needle

I have the same transmission i think. it's from a G-Wagon. where the cable speedo signal is from the transfer case rather than the transmission/gearbox.

I put it in my w123, but i have no speedo output from the transmission, help me please :'( it's blanked off where the mechanical speedoo output should be :'(

Math, see attached photos. The Electronic PU Plug that you'll need to source from a 1980's Mercedes such as a W126 or R107 car that already has a Electronic Speedo. The PU Plug goes into the Socket @ the RR area of the 717.402 Trans. Wire as outlined in previous post

Check this thread here. I made these up for the 722.6 Transmission. But if you have a 110mm tri-lobe bolt circle then at least the wheel will fit and you would most likely need to fab a new sensor mount.

http://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/399988-connect-722-6-transmission-electronic-speedometer.html