this may sound like a stupid question but.....what are the differentials for on vehicles and what consists inside of them under the covers?

gears that rotate the driveshafts or something?

 

ring and pinion...the tranny turns the driveshaft which then turns the R&P to turn the wheels making you go.

 

This has some good drawings and animations:
http://auto.howstuffworks.com/differential.htm

 

so the front diff. on 4x4 trucks doesnt do anything unless it is in 4x4, correct since when my truck is in 2wd, the rear wheels drive it?

 

correct....the front diff does absolutely nothing until it is in 4wd.....

 

i havent used my 4x4 in over a month now, but notice a small 1-2" puddle underneath it when i got home this morning.....hours later, the puddle was NO bigger.

what could be causing it too leak?

i will be keeping an eye on it from now on.

 

lol nice find bob!...

 

again, if a leak occurs underneath the differential, does that mean the cover just has to be removed and new rtv sealant installed or not?

 

There are two common causes of diff leaks: leaking cover or leaking pinion shaft seal. You should be able to see which it is. Fluid leaks often travel on a moving vehicle so you may have to clean the housing first and check again after a short drive.

A cover leak can be repaired by removing it, cleaning the mating surfaces and resealing with RTV. A pinion seal leak would require a new seal and it is a more involved repair.

 

i dont think my front diff. has a cover, so that means it would prob be leaking from where the driveshaft meets the diff, correct?

what part of the diff. is the pinion shaft?

 

It doesn't have a bolt on sheet metal cover on the front? I don't remember seeing a Ranger diff like that.

The pinion shaft transfers power from the front driveshaft u-jount to the ring and pinion gears inside the diff. It has an oil seal where it enters the diff housing. The front diff on a TTB axle like yours also has seals on either side of the diff housing for the axles.

 

The driver side axle beam that the diff bolts onto the back of acts as the front cover.