As far as I now, with the exception of some gassers with a heavy duty towing pkg, most all vehicles combine (not too bright IMHO but cheap) the tranny cooler with something else. Very commonly in the bottom of the radiator. In any case that colocation can case overheating of tranny fluid or whatever other fluid is nearby.
Assuming your system runs fine with the AC off and that your coolant temp gauge is running in the normal zone (ie just a tiny bit left of vertical) I'd suggest:
1. take a look at the front of the AC condensor for excess crud, clean as need be. Check the back side of the AC condensor also; you may be able to do this by undoing the 2 bolts (about 1/2 way down on each side) that hold the fan shroud in place, clip the zip ties that hold the AC line to the 2 plastic pads on the top of the fan shroud, which should (I hope) let you slide the fan shroud up/back enough to shine a light down in that area and flush if need be, put shroud back in place being sure to 1) use EXACTLY the same bolts you removed (accidental use of too long bolts produce instant radiator holes and 2) new zip ties for the AC line.
2. confirm that your AC electric fan is working on both high and low cycle; if it's not working AC performance would be poor and the AC condensor would likely overheat.
3. have a decent AC shop, dealer not necessary, check AC performance for something else that might cause AC condensor to over heat.
4. don't waste money replacing the AC condensor/tranny cooler pkg. Either take the OEM tranny cooler entirely out of the loop or install an extra tranny cooler (http://liberty.eurekaboy.com/transcooler.htm
for example). I suspect with a good oversize aux. tranny cooler there is no real need for the one in the bottom of the AC condensor.
I would note though if your tranny temp sensor is getting unhappy (eg. not working right) just because the tranny is at operating temp, as opposed to actually getting hot, the above may not be enough for obvious reasons.