94 Plymouth Acclaim V6 Automatic with 155K

After a long period of no rain, it rained hard all last night. When I tried to back up the car this morning (still raining), there was no reverse. It was as if the car was in neutral. When I revved the engine, there was no engagement into reverse at all.

So I let the car sit for a few hours, the rain stopped, and then when I went to try reverse, everything worked fine.

Because the problem just happened to occur after an unusual rain, I'm thinking it is a moisture related problem of some kind of electrical nature.

Any ideas?

 

I took it to a transmission shop and they dropped the tranny pan, changed the filter and replaced half the transmission fluid. There was a lot of metal filings on the magnet and the fluid was dirty. I'm wondering if a solenoid in the transmission got temporarily jammed and that's why I lost reverse for a short period. I still had DRIVE. Does the 3 speed automatic transmission for 94 Plymouth Acclaims have a solenoid that is dedicated for REVERSE gear only?