We still have some NOS governors if you need one. However, let me point out a couple details. First, the governor is not voltage sensitive.....in other words there is no 6 or 12 volt governor. It’s a simple centrifugal switch that is normally open. It also doesn’t fade under warm conditions. It either works or doesn’t.
Generally, the symptom you’ve described is a heat related problem with the solenoid. Or a marginal ground quality in the overdrive wiring and physical conductivity of the various metal parts that help complete the grounding circuit. Before spending the money for a new solenoid, try checking each wire connection in the overdrive circuits for good clean and tight connections. Make sure that the two solenoid bolts are tight. It never hurts to add a ground strap from one of the two solenoid bolts to a nearby body surface. Keep this in mind....both the governor and the solenoid require a good ground in order to operate the system properly. That ground runs through the transmission tail housing to the gearbox, to the bell housing, to the engine block, and then through a ground strap to.....the body. See why the extra ground strap could help?
Obviously we sell all of these items but you may not need to replace the electric components. Check all of these things out before you spend your money.