97 Ram Trans Overheats

Have a 97 Ram 1500 4x4, the Trans overheat light comes on (after about 20 minutes of driving) and the truck gets sluggish. Have to manually down shift to pull up a little hill. I have never heard the fan come on either.

When is the last time the fluid and filter have been changed?Also check the condition of the fluid,pinkish in color: good and if it looks like motor oil and smells bad: not good.Chrysler came up with this very dumb idea and will burn up the transmission,a nylon checkball in the bottom transmission line going into the radatior.That problem with the nlylon checkball was that it melts and will plug the line right up.It is in the rubber hose part and there is one thing to do with that checkball,GET RID OF IT! Drill it out or pop it out with a long #2 phillips screwdriver