Usually it's the bearings that wear out.

Chips on the end of the tooth usually don't matter because there never is any contact there.

I just polished them smooth with a dremel so that there can't be any propagation. 

Is that a reflection or large chip on your R(actual 1) picture?


You've labeled the gears wrong.

That's not Reverse and 5, but 1 & 2.

3 and 4 are 4 & 3.


Reverse and 5 are on the other side, and R is usually straight cut.