Transmission has trouble shifting to fourth, staying in fourth, and will randonly down shift out of fourth. It's an automatic 4 speed overdrive and the truck only has 161k miles on it. Any ideas??

 

mine does too but its not at random but i feel like its too early its within spec right at 50 but once it shifts into its seems hard to down shift back i dont know if it the same problem but i feel like we could be in the same boat. or truck...

 

I have a 95 12 valve automatic and it just started shift in from in and out of overdrive. Mainly does it on the highway between 65 and 75 mph. Its not the tps. I was told to have the dealership flash the computer and update it before I started replacing things. Any ideas or solutions would be appreciated