What I found on my 06 Attak was the fitting is getting plugged. Either with crud or may be a little smear from the aluminum cross shaft. There was nothing wrong with the zerk. I found if I removed the suspension and pulled the cross shafts the fitting would take grease. Sometimes just unloading the suspension ( lift the rear end up in the air) would work. My final solution was to pull the shafts and turn down the area near the grease fitting just slightly, .001"-.003". That seemed to stop give enough clearance so you could push the grease/crud through. Worked for 10,000 miles on my 06.