The overdrive is great once you get it dialed in... It has a 33% reduction, so it will enable your flathead six to cruise all day long at 70-75mph.
The cable is a lockout, and does nothing to engauge the overdrive. If the cable is pulled out, it does two things: one, it mechanically disables the sun gear, and two, it disengauges the electrics of the system. The transmission will not freewheel when the cable is pulled out.
When the cable is pushed in, the electrics are free to do their thing, automaically, as you drive the car. Once you reach the cut in speed of about 27 mph, you should hear a click from the relay, and if you let off the gas, the transmission should shift into overdrive. It will stay in overdrive until you are under the cut in speed, or until you kick it down with a full throttle stomp of the gas. The kickdown switch is a two position switch, and is located on the throttle linkage somewhere. The first postion interrupts power to the solenoid, and the second interrupts power to the coil. The coil is cut momentarily to release the torque from the OD, so that the solenoid pawl can release.
Here's a great wiring diagram, that should help find all the wires and electrics (hit reload on your browser if the pic doesn't show):
Also, slide on over the the
http://www.p15-d24.com site, and you will find in the downloads section a scanned copy of the Borg/Warner manual for the R10 overdrive. This book has a terrific step by step troubleshooting guide for the electrics and mechanical parts of this transmission.
Let me know if you have any questions, I might be able to help out...
Pete
http://www.50plymouth.com
