OK, no vehicle likes the cold, but this one had me wondering if maybe there's too much transmission cooling at highways speeds when it's really cold. Is the auxiliary rad under the bumper an oil cooler or transmission cooler?

The car has been working great, but I was driving home from the city on an arctic day (-25C) and after 3 hours cruising at highway speed came up to a T intersection. I pulled the shift lever back to 3rd, but nothing happened. I used the brakes to stop, made the turn, put it back to D and then the transmission was reluctant to upshift through all the gears, hanging on to the gears longer than it should.

Since I was now driving only 80kph on icy roads, it was reluctant to shift to 4th, forcing me to take it to about 3500 RPM and pull my foot off the pedal to finally get a shift.

It's perfectly fine now that it's warmer and on shorter trips. Fluid levels are normal. Is it possible the transmission cooler sucks all the heat out of the transmission under these conditions?

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1993 300D 2.5L Turbo