Overdrive not kicking in - 1950 Commander

[gordr]

Since it's on the bench, remove the solenoid, and insert the blade of a regular screwdriver into the pawl, and twist firmly to engage it. See if you can push it in or pull it out, while also moving the lockout lever. Perhaps something else is interfering with free movement of the pawl or the shift rail.

[chlenz62]

Success! I purchased a box of springs from Home Depot and stacked two of them together to build the approximately correct spring that was missing. The OD lockout shaft is still a little sticky and wants to hang up in the standard mode after switching from reverse to 1st. Nonetheless, the transmission did shift into OD for me. The primary issue was the missing OD lockout shaft spring. I also opened up the speed switch and cleaned the contacts. This is now working as well. All the great support is much appreciated. On the wiring side, I did determine the internal switch on the solenoid is a normal open switch which closes when the solenoid is energized and connects to ground. This doesn't make sense and I'm going to need to spend some time on the OD circuit before I fully understand it.

[gordr]

The internal switch in the solenoid is to provide a path to ground for the ignition-kill function in the kickdown switch. Cruising in overdrive, if you floorboard the accelerator, the kickdown switch is actuated, and two things happen at once. One current supply to the OD relay, which passes through the normally-closed contact pair on the kickdown switch (pair closest to the plunger button) is interrupted. That unpowers the solenoid, but that alone won't kick it out of overdrive, since engine torque keeps the transmission components locked up. But at the same time the normally-closed contacts open, the normally-open contacts (furthest from the plunger button) close, making a path to ground from the ignition points, via the kickdown switch and the solenoid internal switch. Shorting the ignition points to ground momentarily kills the engine, releasing torque on the driveline just long enough for the solenoid to release, opening the internal switch, and restoring engine operation. They say it's about 1/4 revolution of the engine, but I don't know how to test that. When the solenoid releases, it goes back into direct drive (through the roller clutch), and regardless of the position of the gas pedal, it will remain there until the pedal is lifted completely, relieving torque on the driveline, and allowing the governor and relay to again effect a change into overdrive.

The overdrive cannot shift either way under load. The kickdown circuit provides a means of briefly relieving load on the driveline to effect a downshift when needed for passing or climbing a steep hill. The perceived effect is lot like using passing gear in an automatic transmission.

The kickdown switch does nothing when OD is locked out, or when driving in direct drive under the cut-in speed.

[chlenz62]

That explains it! Thank you! I was scratching my head last night, reviewing the schematic, trying to figure out why this black wire circuit would take the ignition points to ground. Outstanding explanation! Thank you!