I have had my high temp warning come up 3 times. Allways when I was working it hard, so understandable.
It sounds like you got a false warning. Possibly a bad sender or wiring problem.
Do you have an infrared heat thermometer? If not, pick one up at a tool shop, and take the temp of your trans. next time out on the road. Check it as soon as possible after you stop.
Here's one on Amazon, but you can get them at most hardware stores......
If you have the 5 speed Allison, you can monitor the trans. temp with a ScanGauge II.
Norman, 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!