intermittent automatic transmission problem - 87 4runner.

I am looking for help diagnosing an intermittent automatic transmission problem on an 87 4runner.
The symptoms are as follows:
Occasionally after running up through the normal gear range then coming to a stop, the transmission does not down shift. To get moving, I have to manually shift down to "1" then up through the gear range.
This will happen just once or twice per trip, sometimes not at all. It seems to occur whether the overdrive is on or off. The AT fluid level is correct and the fluid appears to be clean and un-burnt. The engine is a 22RE (no turbo).
Any help/suggestions are greatly appreciated!
Thanks! Mark
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I'd check the connections to the shift solenoids on the transmission case.
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Ray O
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Thanks Ray,
I checked the connectors and can't find anything obviously wrong. I just noticed that the overdrive off switch has started blinking when the downshifting problem occurs. From what I gather this may be an indicator of a problem with one or more of the solenoids however I can't find a reference for the OD trouble codes anywhere. Does anyone happen to know where I might locate these?
Thanks Again For Any Info Mark
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When the OD off light flashes, it means that the transmission electronic control unit (ECU) has stored trouble codes. You can go to http://techinfo.toyota.com/ and purchase daily or annual access to factory repair manuals.
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