I have a 2001 Dodge Ram 1500 5.9L and my transmission goes on O/D by itself when I start to climb and after it does that for a while the trans. Overheat light comes on so I have to stop and wait for a while then they both go off, any solutions out there for that??

How long has it been since you dropped and cleaned the transmission pan and magnet, replaced the filter, and refilled with ATF+4?