in addition to surlyn's suggestions, I keep OD off any time I am going to be below 50 for long periods, and in NYC, thats often. I have a perma cool rail cooler and I am thinking about upgrading to an even larger cooler, because my trans will still get warm 180 (but not over 180) in long stop and go traffic.
If I turn on my A/C (it turns on my electric fan) I can cool it off quickly