I have a 1955 E7 truck with a T86 gearbox with overdrive that I am having a lot of trouble with. I have done all of the tests on engaging overdrive and electrically, it checks out. Driving at speed, sometimes the overdrive works but usually after about 20 minutes, I can't get it to work. When it doesn't work it still checks out electrically and I have no engine breaking at any speed. I have rigged up a 6V feed straight to the solenoid via a switch and that still won't engage the overdrive. When it works it is great, but I'm wondering if it has something to do with the temperature of the oil (GL1). The kickdown also does not work, although I'm less concerned with this. The kickdown tests all check out. I have removed the solenoid, took the cover off, points are clean and it all appears to be working. I have about a 1/2" of play when the solenoid screws are backed off and I pull the solenoid out. The solenoid engages with the quarter turn. Any ideas? Thanks, Nick