1993 F150 transmission not down shifting

My F150 with 170k miles and an automatic transmission will not down shift when going up big hills. It stays in 4th gear and the engine starts bogging down. I have to manually down shift to keep going. The truck also seem more sluggish and uses more gas. Any suggestions on what the problem might be? Thanks

Will it down shift when you step on it at lower speeds? For instance like when cruising in 3rd at low speed, can you get it to downshift into 2nd or first?

What engine and trans is this, 4.6 L . I don?t know if this is after the change from the AOD with mechanical controls to the electronic AODE.

It is the 4.6L, I am not sure about the transmission. It is mainly noticeable when I am on the interstate in 4th gear going up a long hill. The lower gears seem to down shift fine.