[Jacques Reed]

Hi John,

The keyway end or tang end, as some manufacturers call them, at the transfer case seems to be another thing unique to these vehicles compared to standard Ford vehicles. I don't know why they use them. Perhaps the transfer cases are outside supply to Ford so that is what they are given.

Civilian Ford car and truck speedometers of course are driven from the transmission as there is no transfer case.

All civilian Fords use a driven speedometer gear with a square hole for the shaft. The shaft is flattened to a 0.104" square to go into this hole, same as the speedometer end. This is why no cable from any of the old Ford parts suppliers will work on a Ford CMP except maybe an F-15. They have a standard 20 tooth driven gear with a square hole, which is located on the rear transmission mount as used on 4 x 2 four speed transmissions.

Clark Brothers Instruments catalogue, available online, show some of the fittings used on speedometer cables. The nuts have not changed since WW2 and are still available. Male 3/4-20 UNEF at the commercial speedometer and Female 7/8-18 at the transfer case. Likewise the 0.203" lower tang tip which looks identical to mine and is the same dimensions. I think your connection to Detroit Diesel makes a lot of sense as Clark Brothers supply a lot of instrumentation for the big rigs. These tang tips obviously are used by some of them.
Don't know availability here of their products but at least it is a reference if someone has to talk to a cable manufacturer.

Hope this is of some interest and help.

Cheers,