The fluid was checked at the 65,000 mile service. All was good.
I tried to engage the winter drive function as suggested by TROOPERBC, and it does not engage, nor does the WINTER DRIVE light come on.
I'm wondering if this is a symptom of something specific.
The vehicle has been serviced regularly, and I've never had a problem with the transmission. I've owned it for 3 years now, since about 40k miles. There are no signs of leaking fluid on my undercarriage or under my parking spot.