[rotorwrench]

The electrical part of the overdrive system is "live" as long as the system isn't locked out if you have that lockout switch. It doesn't go into planetary operation until it reaches the governor on speed. My early 1951 Mercury cars were still equipped with the 1950 style transmission and pressed steel half bell. It still had the lock out switch behind the lockout rod on the overdrive tail housing. When they deleted the lockout switch, the system is live all the time. Lock out keeps it from engaging but it is still live.

The rail lock out switch was deleted on the late 1951 Mercury line somewhere in February of 1951. This was the first of the "new gears" type transmissions with the separate cast iron bell housing in the Mercury cars. All other system components were still in use to include the operation relay, kick down switch, function solenoid, and the governor switch. Ford cars used their own type bell housing and clutch so they only changed their gears in the 1951 model year. There were other subtle changes but it's harder to tell the transmissions apart when you set them side by side. On the Ford cars I think they deleted the lock out switch and changed the rear mount somewhat from the 1950 cars. The change on the Mercury cars was a lot different.