I've noticed that when I stop after towing the horse trailer the truck wheels (all 4) heat up to the point where I can't hold my hand on them. This is after several miles of slow (30- 40 mph) driving after exiting the hiway. I have a short up hill climb then about a mile of gravel to my home which I wouldn't think could cause heating - and hardly any braking. The wheels are normally warm when I check them just after stopping but they get real hot within about 5 min.
Is this normal??? What would cause it? Just had the rear diff. fluid changed to Amsoil and everything checked.

The heat from the wheel bearings and brake rotors transfer to the wheels. Thats why they have the pretty holes in them, cooling.

it's called heat soaking, your wheels are working like cooling fins, along with the vented brake disc, and other suspension parts. When you stop they are not getting air cooled any longer, and will warm up. Your engine will also warm up a little once you turn it off, due to the lack of air cooling and coolant circulation.
Hope this helps