My '85 245 automatic started not going into 4th gear. I had bypassed the OD relay last year and was not having any issues until yesterday. Shifts fine from 1st to 3rd, but won't go into 4th at all. Fluid level is perfect. Any suggestions where to look next? The car has 265K on it and runs great otherwise.

Thanks.

No one will believe this, but I needed a 16amp fuse the other day and pulled one from the one that runs the rear defrost AND THE OD. Forgot to reinstall. I have my 4th gear back. I ashamed to admit this, but here it is.

Last night I changed a dead solenoid. Before removing it, I tried to clean behind it, but didn't try hard enough, apparently. There were some pretty big rocks rolling around on that exposed surface. Still no 4th gear. :(
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Art Benstein near Baltimore

He often broke into song because he couldn't find the key.

I bypassed the relay. I' pull and check the solenoid and clean it too. Thanks, didn't think of that.

Did you bypass the relay or the solenoid?

Three things normally fail specifically in OD actuation:

Relay solder joints
Wiring under the car to the solenoid
Solenoid itself

If you had mentioned it slipping it could also be the clutches in the OD unit but I guess it could still the seals (an uncommon failure).

Could be that something is plugging the small hole in the bypass piece. I would remove the bypass and check to see if something is plugging the hole.