i have a 1993 dodge dakota with the v6 magnum engine, 4x4. while i was driving down the road i heard noise coming from the front end like something popped. luckily i was close to home. i looked under my fender and saw fluid everywhere, so i checked my oil,tranny fluid and anti freeze. everything was in normal range. so then i checked my front axle and saw that the plug keeping my gear oil in had came off. my question is what caused that and how much damage could it do?

correction, i believe its the differential plug

It could do a lot of damage but if you didn't have any problems and put the plug back in you should be good. What I don't understand is how it popped off in the first place. Which differential was it?

make sure you put fluid back in the diff before you put the plug back in. I've never heard of the plug just popping out like that. you may want to take the cover off the differential and look for any damage or metal shavings in the bottom while you're down there.

It could be possible that the diff was way overfilled and the pressure of the extra fluid along with an old or damaged plug caused it. I believe there is only a fill plug and not a drain plug on these diffs, so no fluid should come out with the plug out while on a level surface.

Your vent hose is clogged. There should be a vent hose on top of the axle somewhere. Blow it out. That will cause exess pressure to build up and blow off your plug.

its the front differential 7.25 inches and 3.55 ratio. i had the cover plate off yesterday and my ring and pinion gears are stripped. im looking at about 300 for the gears plus probably new bearings and etc kit. and it has only the fill plug like (inuchan187) said.