The axle thrust button is used with the stock tapered axle bearings. There has to be a way of adjusting one side (right side axle retainer was adjustable from the factory) that tightens the race/ bearing assembly. When you screwed the adjuster in on the right side, it would push the entire axle up against the thrust button and therefore push the left axle outward and eliminate the play in the Race/bearing assembly on the left side.
When switching to green bearings, this adjuster is not needed since green bearings are fixed race/bearing. When you bolt one axle in you will not be able to bolt the other side in because of the thrust button, it just won't allow the second axle to slide in far enough. The only solution is 1) remove the thrust button. Which is a little more hassle because you have remove the third member, take the Sg apart to remove the trust button. This is on a cone style SG. If you have a clutch type you can remove the trust button with just removing the third member and working form the axle shaft holes and drive the roll pin out from one side. These are three piece thrust button on the clutch style. One piece on the cone and open carriers. 2) or the other solution is to shorten each axle by aprox. 3/8" and leave the thrust button in.
