Would you say that these 17 year old solenoids were leaking ATF?According to the A/T troubleshooting guide in the service manual, the best description of my symptoms was "excessive shock or flares on 2-3 upshift or 3-2 downshift", and the first thing on the list to check/replace is the shift solenoid valve C, which is the lowest one underneath the starter, and doesn't require removing the starter if you want to access it from below. But because I have had a few other random shifting issues, I wanted to replace some of the other valves too, so going in from the top was necessary for getting to the other 2 shift solenoids. Removing the starter is pretty easy and gives you so much more room to work. So it could be that all I needed to do was either replace the shift solenoid valve C, or clean the filter on the clutch pressure solenoid C, but I didn't mind spending a few extra minutes and a few extra dollars to replace all of those rusty 17 year old parts. I will probably still remove and clean the A/B solenoid unit since that's the second suggestion on the troubleshooting list. It's right next to the transmission filter, and I think I want to do another drain and fill and change the filter after swapping all these valves, just in case I accidentally introduced some dirt into the system. I'll take some photos next time I'm doing that.
Sounds like a job for a can of spray Degreaser and a can or two of CRC Electronic Cleaner for wiring and conections.