can you run an auto tranny too cold?

[hayjayhorses]

I am woundering if I am running my tranny to cold. F550 4R100 7.3. I have 2 tranny temp gauges one in the line going to the cooler, about 10" from the tranny. The other in the pressure port.

In this cold weather 0-30 degress the temp on the tranny line will not go over 100 unless i am in stop and go traffic with a good load on (no locking of TCC) the port temp getts to about 135, I think a lot of the pressure port temp comes from the engine via the aluminum tranny case.

I travel from Massachusetts to New York a few times a week (500-600 miles round trip) The last few trips with the ECT temp @ 170 to 180 (thanks to a peice cardboard covering the grill) the line temp stays below 100 and the case temp less then 135

When i pull a hill loaded the line temp will get to 140ish and then right back to under 100 on the flat

I put the largest tranny cooler I could find tru-cool LPD4739 in front of the ac condenser, witch is not getting direct wind (custom cardboard grill cover).

Han I harm the tranny by running it too cold? ATF getting to thick?? I am using mercon 5 tranny fluid. I am going to put amsoil ATF in it in a few weeks.