Ive got conflicting info about auto trans coolers and in-radiator cooling. I'm doing an auto swap and have been told that I need to include an in-radiator setup for both cooling and heating in cold weather, plus an external cooler for warm weather rock crawling. Anyone have experience with an auto trans without running the auto fluid to your radiator in cold weather? I'm talking about + zero temps. I know I need an external cooler for rock crawling, but really don't want to buy a new radiator for cold weather. Also, any recommendations for a cooler? IE finned cooler vs coil type cooler. Thanks for the input.  

I had a 95 yj with a 400 chevy and th350 trans I ran it in Indiana winters for about 3 years I never had any trouble with just a after market trans cooler only.  

The biggest killer of automatic transmissions is heat. They don't have any problem heating them selves up.

While it may be true that there is some warming in the radiator trans cooler, it's not really the intended functionality.

On a cold morning, you could drive several miles before there is any heat in the radiator.  

To finish my point in my previous post. The radiator does help with a moderating of the trans oil temp. Since an older trans does not have any kind of a thermostat, the temp of the radiator fluid will help keep the trans oil in an operating temp range.

Some newer trans monitor the trans temp oil and adjust the shift pattern accordingly. Some new trans also have a thermostat for the oil. Older trans just have a firmer shift until the trans oil warms.

An additional cooler will help moderate the temp on hotter days even better and is a good idea.

Good plumbing is the trick for a good external cooler. Spend the money and effort on good lines with good fittings.  

I do think it is a good idea to have a radiator with an auto trans cooler provision to help keep the trans oil at a more even temp year around.  

If you go junk yard shopping you'll find some good stuff. You might find a radiator that has an auto tranny cooler.

But more importantly, you'll find your external tranny cooler. This will either be in the form of an aftermarket one that somebody installed or an AC evaporator. The AC evaporator is under dash, not the condensor, which is located in front of the radiator.

Evaporators come in many sizes and are a great air to liquid heat exchanger.

Another place to source a cheap AC evaporator is the metal scrap yard. They recycle AC units. The evaporators are easier to remove and they'll just charge you the scrap weight. The window type room AC units are what I'm talking about. Couple bucks at most. The junk yard guys might think the evap is worth more than just scrap.  

Thanks for the info guys. I think for now I'll go with an external cooler and take it from there.