Where is your gauge getting this reading from? If you tow, and I mean really tow your trans is going to get warmer than 140, period, I don't care how big your trans cooler is. I have one of the biggest coolers you can have, and still see 160+ if I work it. You also might have a bad gauge itself. I am not going to argue this with you, it's just that 140 is to low for a 4r100 that is being worked.
NCH