Transmission oil inspection time: See that little yellow ring on the right? Well it is supposed to be attached to the yellow wing nut. The yellow plastic wing nut. This is a diesel transmission, and they used a plastic wing nut on the dip stick?
This looks like something designed for a lawn mower. The fracture occurred where the threads begin, where the o-ring seats — where compression turns into shear. This apparently is a common problem based on searching the cruising forums.
So now, we have a new one on order, and I have to extract the fractured piece in such a way as not to get any fragments in the transmission. This is where plastic may work in our favor. A slot screwdriver firmly pressed downward while twisting should do it.