After inspecting the bellies of a few 240s and 740s in the boneyard - none have my speedo gear unit in the tranny. My 1985 245 has a speedo cable running to the tranny where it plugs into the gearbox and the tranny gears spin a little speedo gear that controls the dash gauge.
On my 1987 740, the rear differential has an electronic sensor instead of this gear driven way.
I haven't even looked to see what tranny I have on the 1985 245 (automatic), but is my gear driven system something specific to a particular transmission or date range? None of the other 240s and 740s I've checked even have this.
Jamie