2000 Dodge Ram 1500

My truck, 4 years old, decided it didn't need it's tranfer case oil. Seal leaked out all fluid and now getting rear end loud hum while driving. Stopped driving and taking it in Monday 1-3-05 for repair. Any idea why a 4 year old vehicle would have such a devastating (and potentially very costly) problem. Anyone had this problem before? Any help would be great! Thanx!

Yikes, I'd have stopped driving it when the fluid got out.

How many miles? Lots of offroad time? Are you the first owner?