I have 2000. 114k I noticed a little moisture on the front diff. a while back. The front diff. has become increasingly wet as of recent. Like the whole pumpkin looks like someone poured a quart of oil on it. I am now noticing a slight click coming from the diff. when i first tap the brakes. Like a weight transfer kind of thing.
There isn't any leaks other then my radiator which leaks on the other side of the jeep. I can also see a light colored oil on my transmission pan area too. Maybe from the front diff. There's a seal behind the differential universal joint that looks quite wet.
What seal could be leaking?

 

Could be pinion seal, the breather hose came off the diff or the diff cover gasket leaking

 

Thanks for the avenues. I'm going to say its the pinion seal. Seems like that's where the oil is built up the most and looks freshest. But, i'll be checking the rest as well.