I don't have any info on OBD-I Explorers, so I can't help with any specifics.
If it were mine, I would get under there and open all of the transmission electrical connectors, clean/dry them out and apply dielectric grease to the pins before reassembly. Also do the same at the transfer case VSS connector. It might fix the problem and, even if it doesn't, it is not a wasted effort. You need to waterproof all connectors under the truck for use in wet/muddy conditions