Not sure if you figured this one out yet but I had a similar problem this past weekend. Here are the details:
1) Overdrive light flashing on column shifter
2) Transmission in failsafe/limp mode
3) seems like it is stuck in 2nd or 3rd gear - sluggish to get going, almost seems like a misfire in the engine and top speed is around 45 - 50 (3500-4000 rpms)
4) OBDII reader showing around 11 codes, all related to shift solenoids, transmission circuit, O2 sensors, etc.
After a ton of calling around, searching online (including this forum) I was able to narrow this down to two possible causes, both of which were electrical.
It was either the connection at the side of the transmission (which could be external or internal) or there was a short/break in my wiring harness between the transmission and the PCM.
I traced mine back to the latter and found my wiring harness partially melted from contact with my exhaust manifold with two of the internal harness wires fused together. This was causing the transmission control fuse (fuse # 23 in the engine panel) to blow and generate the failsafe mode on the trans.
Some careful separation of the melted/fused wires and ton of electrical tape as well as zip ties to ensure the harness can't come in contact with the manifold any more fixed my problem. I know there were a lot of similar stories on here about the same issue so I would start there.
I'll answer any questions I can because I have read stories where folks spent a ton of money fixing "other" problems that didn't resolve the original one.