FYI...when I was assembling mine, I kept having the same issue, but it is because I found the front axle/bolt is a little bit shorter. I put the right one in and it worked fine. I never measured them to see, but definitely would do as you stated with the nut and hole if I used the wrong one. Easy to tell the front axle from back for me as the rear axle was much more discolored due to wear and grease etc. I would try the other axle to make sure before grinding etc. Good luck