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Q: auto trans on 1991 Ford Explorer

91-4x4 explorer auto trans shifts in to over drive then won,t shift back in ghanged sencore on trans still no luck someone told me the valve body needs rebiult .help me pleas
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I'm unclear as to what you changed on this A4LD automatic transmission. A sensor?

Keep in mind this transmission is NOT primarily electronically controlled. It uses engine vacuum to control normal hydraulic shifts. The only item that has electronic control is the torque converter operation. The torque converter clutch is controlled by the engine processor (PCM).

I would be focusing on:

--fluid and filter condition - needs changed?
--engine vacuum pressure - check the vacuum line, check the vacuum diaphragm.
--Operate the transmission without overdrive - see if your problem remains or if it's gone. (you should have a gear selection for just "D" not "OD").

Let me know what you find out. Good luck!
i re placed the vac modgule on the trans now it in out of over drive on the hyw . darn ford .lol.
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