Four Speed Backup Light Switch – They Did Exist!
The first design of the 4-speed synchronized truck transmission, introduced in 1948, was used through about 1965. About mid series, when the dealer installed backup light increased in popularity, a special switch was attached to the base of the floor shift lever. This was the only location possible as there is no external linkage on a 4-speed.
No doubt regular floor contact with shoes and boots shortened the life of this small electrical switch.