I broke an old Taurus radiator apart one day just to see the AFT cooler. It was a tube heat exchanger about 2" diameter and 12" long (the coolant flows though the middle and surrounds the outside). It looked like it could quickly cool the ATF down to the coolant temp. Only thing is the coolant temp may be 190F (a cooler t-stat would help that).

I was considering removing mine from the loop (I'm adding these right now pics ) But I'm thinking in cold weather the radiator loop may actually help warm the ATF to keep it from over cooling and resricting flow. If you do remove it (or even if you don't) I'd use one or two of these self regulating coolers: http://www.importperformancetrans.com/coolers.shtml especially in a cold climate.