For 4x4 low you need to STOP and put the trany in NEUTRAL then put in low only in extreme conditions. 4x4 high you can put in at all speeds to a certain 50 mph as far as auto 4x4 that is auto trac as we were saying.. it knows when there is slippage in the tires/differental I keep a strap and just a regular safety kit. flairs,firstaid kit, triangle. My F250 has a 12000 lb winch, but thats another story..for a flat..find some wood to stabilize the jack in the sand. hope this helps.. I have 3-4x4 trucks and believe in them!