(05-17-2010, 05:43 PM)ForcedInduction The W116 used mechanical.
Sorry, I meant W126. Good to hear the W126 speedometer heads are all electronic, there are some good pictures of a W126 speedometer and instrument cluster in
this thread. It looks like I'll be able to cobble it together, I think I'll just go buy one and figure it out. The plan is either to try to hook something up using the speedometer cable to drive a device that will send either a pulse or a voltage signal to a board which will convert it to the appropriate signal for the speedometer, or just generate a pulse directly from the drive shaft or some other rotating driveline component. One idea is to hang a hall effect sensor near the front flex disc so it pulses each time one of the 8 bolts passes by. I would rather do something a little more "solid" like interface with something in the tailcone of the trans, though..