Another difference that I believe is common is how your arms move when you walk. I was diagnosed at a young age. I found out I didn't swing my arms normally when walking after someone made fun of me for it in high school. I had to consciously think about swinging my arms for a while to figure out how to do it right. I still catch myself sometimes not swinging my arms correctly when walking or one of my arms resting at a 90 degree angle (T-rex arm).

I'm not sure if it's the differences in gait that might cause people with autism to need less arm swinging for balancing or if swinging less causes them to develop those differences in gait.