the internal coil in the rads is a 3/8" Thetight coils in the ran do become tight. Some rads have a actual heat exchanger plate style trns cooler in the rad.

Honestly in the warm enviroments you american are in the trans cooler idea is horible. Your pushing trans fluid thru it at XX temp and if its lower thn 180-190 you are warming it up. Thenit comes out at 180-190 and goes back to the trans or if you have a frn mount it will lower it down 30-40 degs. Ive removed the rad cooler completely in a bunch of cars and the trans temps drop pretty noticable. Just let your trans warm up in cold weather before beating on it. Clutch packs and bands dont like suppr hot fluids. Trans fluid is like a coolant remeber.

My dads LLY we eliminate the trans cooler in the rad and drop 20-30 righ off the bat.

All my auto cars and trucks dont run the oem rad cooler. I think its fine for your grocery getter but thats it.