See this very long thread on Ultra lube axles--
Ultra-Lube Axles and Bearings Procedures
Read post #1 for PDF links to various axle manuals.
You can also order bearing/seal kits from etrailer.com
The grease travels from the grease fitting (called a zerk) thru a hole drilled down
the center of your spindle and exits out a hole in the side of the spindle that is
located just behind the inner bearing. This puts the grease coming out in between
the seal and rear or inner bearing.
For clarity we call the bearing that is closest to the end of the spindle
and closest to you when you're sitting in front of the hub the outer
bearing. The bearing that's farthest away from you is the inner bearing.
The grease hits the seal and can't go that way (we hope!) so it must travel thru
the inner bearing, filling the hub more or less completely and finally out thru the
outer bearing where you see it around the end of the spindle.
IF you know the zerk is OK there is a blockage between the fitting and the
exit hole in the spindle. Could be burnt grease in the spindle or the seal or rear bearing
is somehow miss-located so it's sitting over the hole.
IF you really want to get to the bottom of this, I suggest pulling the outer grease/dust
cap. Remove the cotter key and spindle nut and washer.
Pull on the hub gently and rock it side to side.
This will cause the outer bearing to slide out where you can get
it with your fingers. Pull the bearing off the spindle with clean fingers
and lay it aside on a clean paper towel.
Pull off the hub.
You probably don't need to remove the rear seal and bearing. Pump some grease
into the fitting with the hub removed. See it come out the little side hole near the
seal area in the spindle??
IF you go this far you will probably be able to find out what's blocking the grease.
You should have papers with your trailer that are from the axle maker that tell
how to change bearings and adjust brakes and so forth.
If you don't have papers, you can find axle maintenance manuals online.
Tell us what axle you have and someone can point you to the PDF file for your
Please drop back and tell us what you found.