Most Jeeps: Transfer case in Neutral, transmission if gear (I use 6th gear) or Park if automatic. Jeeps that do not have a transfer case Neutral position usually can not be towed four down. Jeeps with certain transfer cases can not be towed four down without modification to stir up the lube. I do not remember which ones, but I bet it can be found in Google. Some Jeep four wheel drive systems can not be towed four down, period! Read and follow the instructions in the Owners Manual.
A manual transmission does not mean it can be towed four down. Some transmissions will self-lubricate, but many will not. If not lubricated, severe bearing damage may occur in time. This can be alleviated by stopping every 200 miles or so and running the vehicle in Neutral (clutch engaged) for a few minutes to redistribute the lubricant. (I did that many years ago towing a 1963 Corvair Spyder from Northwestern Montana to Seattle.)
