That was happening to my bronco a few months ago. My filter was filthy and causing the oil to boil out of the dipstick. Replaced the oil and filther. Added some lucas tranny additive and Added a transmission oil cooler. Been running strong ever since.
Make sure your xfer case and transmission are at proper fluid levels. Id recommend full sythentic. is your heater stuck on? if it blows hot all the time, it might be a stuck heater control valve on the top of firewall under hood.
Where do you feel the heat? When did you notice? While you're driving, inside the truck (footwell, console area)? Or do you mean you're out under the truck at the actual tranny and xfer case?
Fluids are a good start.
Xfer case takes 1.9qts of 75w-90, preferably synthetic.
Tranny takes ATF. Drain out all the fluid thru the drain plug. Your A343 might drain like 5ish qts. Measure and refill the same amount thru the dipstick. Always check tranny fluid level with the truck running. Either check cold with COLD or hot with HOT level.