Ok, so I just did this replacement last week, and after getting it together and installed the "2" o rings together before that shaft with the two large nuts on it. That is probably where your other o ring you have extra goes.... anyway, I got mine together, but there is still some slop and the axle is shifting side to side now! Crap. I used 2 different o rings though because the ones that I had were destroyed, got the new ones from a auto parts store. Could they be the incorrect size is why I'm getting the slop? Or is it that I just need to tighten everything again after a ride?