Google shows me a few forums posts about this : here at JCC, at JeepGarage and CherokeeForum (KL section). Members who posted never returned with follow-ups. Some had their PTU and RDM replaced with no success. Like you say, this system is sensitive to heat often caused by excessive wheelspin. 4-Low helps if you have it. Good winter tires should help here (don't know if OP has some) to minimize wheelspin.They will overheat with heavy use, and need to cool down. It will be fwd until it does. It has nothing to do with engine or transmission temps. Do you happen to have a low range? If so, use that in those situations as it locks the front and rear axles together. Once it overheats, you need to give it time to cool off. Shouldn't take too long with it being 19 degrees outside, but you need to let it sit and not keep trying, or it will keep heating up.
Letting it cool down is the only way to get moving again, for sure..