Could you draw a construction line circle around the outside of the gear, dimension its diameter, move the dimension to the section view, then hide the circle?
You can show the dimensions of the angle by moving them to the top of the view instead of the bottom.
The software is showing the dimensions it knows about. In your section view, the OD doesn't exist, because the section cuts through a tooth at the top and a gap between teeth at the bottom.
It might work...
Thanks for both.
The aligned section view works for me quite well.