We have a 2004 Dodge Ram 1500 with a 4.7. It is heating up and when we back it up it smokes. Any ideas?

Check the operation of your cooling fans. It may be a bad engine coolant temperature sensor, fan motor, or fan relay. It may also be smoking (actually water vapor in exhaust) in any gear, you just notice it more backing up since you're now backing into your exhaust. Water gets into exhaust normally as it is a byproduct of combustion but if it becomes excessive enough to produce "white smoke" you should check for coolant leaks through the head gasket. Basically you need to do a thorough check on your cooling system, check fans/relays, check for hydrocarbons in coolant with Block Tester, pressure test cooling system for leaks. If you suspect a head gasket do a compression test.

The fan comes on as soon as you turn the truck on. Is that the way it should work, or is something wrong with it?