What I now know about tag axles.....a clean, well greased, new sleeve, healthy tag is very easy to move. Without the drum attached or the shock, a 15 yr old can lift the tag axle because it moves so easy.
No amount of cleaning or flushing from the outside will get the inside grooves clean. You must take the tag axle out. Infact, if just one of the 10 grease holes are open on the axle, when you pump grease you think you are lubing the whole axle... when in fact.... you may only be lubing a small section of it.
Now that I have depressed you....
When I told my boys we had to pull the other side, they both swallowed hard.