Speedo Gear O-ring or not?
 

So I pulled my speedo gear out of the transmission tail shaft this weekend to have a look. The gear looks good and appears to function fine....should there be an o-ring between the nut and the threads where the gear attaches to the tail shaft? I did not see an o-ring when I removed the gear. The gear had a dab of green paint on it....would that indicate the gear size/ratio?