Thanks for the suggestions. The transfer case seems to work fine. Other conversations on this site suggested disconnecting the battery for 5 minutes and see if that re-boots the system and turns off the light. Others said that does not work. I was going to try it today, but the Service...
My 2020 Gladiator, 6 speed manual, got the recall "fix" to the clutch a while ago. Prior to that, in five years I had never had the "Service Transmission" message come up. Since the "fix" it comes up frequently, and then goes off after a while. It sometimes takes a day or two, but it always...