i bet yer not doing what just about everybody else is guilty of. JACK THE AXLE OFF THE GROUND! this needs to be done every time you lube to make sure the grease flows around the entire bushing, not just in one spot. use a propane torch to get the axle warm, let it set for 5 minutes for the heat to soak to the bushing, then try to grease it again. if it breaks loose be sure to pump in enough grease so that the grease that comes out is the color of the new grease.
nobody jacks the axle off the ground anymore, but doing so takes the preload off the kingpin so the grease goes all the way around. the fact you are having this problem is an indication that maybe the thing hasn't seen grease as often as it should, so after 100 or so miles, grease it again to flush out what's left of the junk grease. overkill? maybe, but if you don't have to replace kingpins it's sure worth the extra effort.
