New information time.

I checked the fluid level a few times, and it seemed a bit low. However, I do not have a pyrometer, so I'm not sure the the fluid temperature was correct.

After driving about five miles, the level showed about 5mm below the add line for the low temperature scale. After driving on the highway for an hour, it was about 5mm below the add line on the high temperature scale.

I added 1/2 pint of fluid to the transmission, and now it seems to perform as it should, regardless of the temperature in the morning.

I'll probably do a fluid change in the spring anyway.

To correct a comment in the original post: according to the owner's manual, this transmission always starts in first when a forward gear is selected.