I am having problems with the overdrive on my 1987 240 wagon with automatic transmission. About a month ago the car quit going into 4th gear (OD), as though the lockout button had been engaged on the shift lever. The light on the dash would come on and off as the switch was operated, but it would have no effect on the OD. I removed the solenoid and checked it by applying 12 volts directly to the solenoid, and it did not operate, so I assumed that was the problem and bought a new one.

While installing the new solenoid I decided to check the voltage from the wire to the solenoid to see if the switch and relay were working. I initially found that I had 12 volts on the wire all the time, no matter the position of the switch. Also the light on the dash had quit coming on when the switch was operated. The relay was still clicking, but I decided to crack it open and see what was going on inside. I found a bad solder joint on the back and re-soldered it. After I did this I would get 12 volts at the wire only when the switch was off, and the dash light would come on when the switch was on. I put it all back together and everything appeared to be working great (dash light on when supposed to be, solenoid clicks when switch operated).

I road tested it that night and everything was working fine. The next morning it was back to no OD. After about 15 minutes on the road it eventually goes into OD. The light on the dash still comes on with the switch, and after it goes into OD the switch will kick it back out when engaged.

I am out of ideas, and am planning on doing the dremel surgery to my old solenoid to remove the circuit from the equation. Does anyone have any other ideas of things I could check?

Thanks