Took it to a transmission shop in Cedar Hill, the guy is a friend of Katie’s Dad. He took out the engine speed (RPM?) indicator and found it clogged, so he cleaned it up and put it back and all was fine.
Driving it back home tonight, I found that it’s still doing the same thing it began doing yesterday (before all the flashing lights started going off). When you’re cruising around 70-75 and going up even the slightest hill so there’s resistance, the tranny seems like it can’t decide if it wants to be in drive or overdrive. It acts like its starting to downshift, seemingly disengaging the clutch slightly enough for the RPMs to rise by about 300-400, catches up with itself, and seemingly reingages the clutch so the RPMs go back down. As long as you have your foot in one place and it has a little resistance (like going up the hill) it continues this cycle. If you press the gas or the hill is too steep, it will downshift into drive (which can be confirmed by pressing the OD off button, usually used for towing.
I don’t know what the deal is, but I’m gonna try my best to just forget about it until this DSP final is out of the way on Wednesday; hopefully nothing will happen with it between now and then.