On a recent trip, my Expedition suddenly stopped shifting into 4th gear. Now the O/D light is blinking which apparently indicates that a transmission trouble code has been logged. The 2-3 shift is also delayed and hard.

My generic OBDII reader does not sense any engine codes (which I also suspect could be normal since transmission codes may be read separately).

I'm waiting for a shop appointment. What's the chances that I could get out of this without a total rebuild? There's 130K on the orginal trans, so it wouldn't be a total surprise.

I see a lot of posts regarding sensors, but nothing matches my symptoms exactly.

Thanks.