As I understand the manual, the over drive solenoid has a constant electrical/current flow so when you push in the cable the overdrive lever opens up for the pawl to engage the reduction gears if the governor has reached the appropriate speed 26 mph or so.  In other words the solenoid is active most of  the time or have I over simplified the function. . Does this cause problems in the solenoid.  Is it prudent to put a switch into the ignition line to the overdrive relay so you can control the electricity on or off.  These solenoids are expensive and hard to find so I thought any current relief will help prevent failure.  

Finally does anyone rebuild the solenoids.
Thanks,
Richard