Speedometer gear wear

I see the gears have smaller or larger diameters depending on the amount of teeth. It looks like the length and the friction on that surface is what holds them in postion against the output shaft. It makes sense they are plastic, because if they were metal with out a bearing or bushing the wear would be tremendous as opposed to the minor wear we're seeing from the plastic shaft. With this in mind the wear is probably normal and making the shaft shorter may cause a problem rather than alleviate one.
Thanks