Mine drops the temp about 20 - 30 deg F when the car is moving. That'* from an inlet temp of 180 F. In the winter the coolant radiator heats it up because it is in series with the original cooler inside the radiator.
I do not think it cools it down that much though on a hot day when the car is idling in traffic. My fan temp switch is still original, so it doesn't come on until 195 F, which is almost never. I want to get it reprogrammed soon to come at 180.
For every 10 deg drop you double the life of the fluid.
But I change the fluid every 25,000 km regardless. Like I said, it'* good cheap insurance.

I was told that the lines going from my transmission to my radiator were transmission lines but I dunno I took the guys word for it and havent checked. There was even a safety recall because the lines would come off and spray fluid and catch on fire if to hot.

I dont think cold temperatures will harm a transmission. They would have to be very very cold to make the viscocity cause damage. My transmission always shifts better when its cooler outside and when I am driving during the winter. Summer time it sucks

you know I'm running a tranny cooler!

My car (97 SE) is having problems with burning the tranny fluid. I just had it flushed and a new filter, and 6k miles later its hardly even pink anymore. When it got changed it was dark brown and smelled heavily of burning (might have even tasted like it). So, I'm thinking a tranny cooler would help me in my case. I want to say that obviously there is some problem with the transmission that is causing this, but I can't get the dealership I get it serviced at to find anything wrong without paying them to take it apart (which I want to avoid). I guess after a tranny cooler, and probably another flush, we'll have to see what it does.

Going back onto the original topic for a sec "Colder T-Stat Myths" I've realized some info that might be interesting to those of you with a plastic intake. This is up for debate and I have no proof other than what seems like common sense but please correct me if I'm wrong. A big problem with these intakes is a crack showing up right? So it would seem to me that colder t-stats and ESPECIALLY drilled t-stats will quicken this problem. Cracks show up due to quick and fairly drastic changes in temperature, we all know this. Put a glass in the freezer then pour hot water on it, see what happens. I'll use a drilled 180 t-stat as an example. So your car is originally set at 195 and you want more power (which as you remember doesn't do much in a n/a car anyway) so you drop in a drilled 180deg t-stat. For all intents and purposes having your t-stat drilled throws the 180deg part out the window because you will always have some free flowing coolant so now its a "Whatever temp your coolant is" t-stat hehe. So anyway...So your sitting at an extremely long light and you watch your temp climb up to 210 or just before you fans kick in. Then immediately you merge onto the highway and watch your temp (depending on weather) drop to 180 or less. Isn't that a pretty quick and drastic change in temperature? I know this because I have a drilled 160 t-stat and in the winter on the highway I've seen it drop to 150 or below and hold. So assume if its cold outside your drilled 180 will hit 160 or 170. Thats a change of 40-50deg in a matter of a minute or so and can't be good for the plastic intake. I just thought of this the other day but it seems logical, no?

Some good thoughts but the plastic intake cracking is time related due to the plastic breaking down by the high 195 - 210 deg temperatures. As the plastic ages, it gets brittle and cracks at the stress points.
Running with the 180 stat will either delay the problem a lot longer or eliminate it.

mhmm...I can see how colder would be better but unless your fans come on earlier your running into the temp change problem...or is it a problem?

The high temp stress is right. Most of the failures are at the EGR port, aren't they?

The drastic temperature change occurs in the coolant. It takes longer for your engine parts to change temperature. Its definetely not like putting a piece of glass in a freezer...

I am in Michigan and basically have the same weather as you. I understand exactly where you are coming from there. The IDEAL transmission cooler setup would be a small transmission cooler mounted in front of the radiator, but with a Thermostat or a driver controlled switch and guage. That way if it had a thermostat it could open and close with the temperature like the engine thermostat does, that way it never gets too hot or too cold. The thermostat would be more ideal because it would be automatic and the driver could lose attention or forget about it and not turn it on. But the driver controlled switch would work if you wanted to turn it on and off all of the time. You would have to have a transmission temperature gauge in the car, and when it hit a certain temperature (180-200*F) the driver would turn the switch on, then when the temps went back down to like 160 or 180 they would turn the switch off. But, I am thinking that if someone were to install a tranny cooler with a 180 degree thermostat it would be ideal. That is probably the only way I would install a tranny cooler on any car I owned.