01 Ram 1500 Short Box 5.9 L 4x4 3.55 gears 50,000 miles.  A couple
weeks ago I noticed a leak coming from the rear end.  At first I
thought it was the gasket around the cover.  After I wiped everything
up I have notice that the rear end is starting to get leak again.  Took
about two weeks to reach this stage.  It seems to be leaking slowly
from the u-joint area into the rear end.  About 3 years ago I changed
out both u-joints on the drive shaft.  The rear one started to make
noise.  I made sure to put greasable ones on.  What would cause this
leak, or what other measures should I take to know if this is a big
deal?  The fluid is checked every 3,000 miles at a local oil lube shop.
Appreciate any help or advice.