I have a 2004 ford explorer with the transmission problems that everyone has? what is the fix?

The same problems as everyone...hard shifting in and out of reverse. The overdrive light flashing. I've seen online that this was a really common problem and people were having a real hard time figuring it out. people were on their second and third transmission!?! I know Ford tried to say it was the fluid. I can't find any recent talk about it though. Anyone know what the final problem was or what the fix is?