W123 Speedo Question

[GREASY_BEAST]

Hey all, I'm in the process of brainstorming all the little things I need to do for my rear-end swap. The plan is to swap in a 2.47 rear off a mid-80s W126, and I am wondering if the 160mph (I think?) electric speedo from a gasser benz can be put in my car, a 1984 300TD W123 wagon, that currently has a mechanical speedo...

Questions:

a) Will it screw into the stock instrument cluster?

b) Will I be able to install the electric sender unit and cable on my tranny?

c) How do I go about doing question b?

[babyjames]

I was told it is impossible to interchange instruments/transmissions between W123 and W126 chassis.

The speedometers on these cars are never accurate, anyway, so I wouldn't sweat in too much.

Jay.

You can swap the tail housings on the tranny to get the electric sender.

Using the speedo is a much harder task. There is one member here that got a W123 speedo to work in a W126 SEC, it *might* be possible to do it the other way around.

[GREASY_BEAST]

Thanks for the info, looks like I'll be using a GPS and some testor's model paint

[OMEGAMAN]

If you have a wiring diagram for the 126 we might be able to find out what powers up the speedo and use that part on the 123. I'm guessing the speedo uses less than 12v.