Countershaft Question

Well perhaps I was hasty. Its just that in the hundreds of those trannys I rebuilt There was never ever any evidence of that O-ring leaking. But then that was in the late 70s, and the trannys were "nearly new".
I have never used an arbor to hold those needles in. Grease works very well. Not vaseline, not lithium based. Good old gun grease. The needles come in the small parts kit from Ma.