Hello everyone! I just got a 1985 300ZX, auto trans (non 2+2).

I was diagnosing some issues with Overdrive. It seems to not kick on after 3rd gear. I know this is probably the solenoid that tells the ECU that the trans temp is good enough to engage it. If I turn on cruise control and activate it on highway speeds, it shifts into overdrive no problem. It will never do it on its own though. I have looked through posts and tried to find the part so i could buy it, but i am having trouble locating exactly what i need.