Trans problem, late shift from 2nd to 3rd

95 Sable, 3.0, dont know what trans. Runs good for the miles on it 212K, dont know how old trans is. Basically it shifts good up to the shift from 2 to 3, then the shift is so long the RPM's rev too high. Eventually it does go into 3rd. Getting on the xway is tough because the shift is soo late. And of course when it does shift to 3rd it kind of shifts hard.
I have been just holding the car and now must decide to scrap or fix. Doubt anyone would buy a car with those miles and a bad trans. I cant lie about it either and just sell to someone. So I would like some opinions from anyone with trans experience.

I have a 99 sable,, i have the very same problem, it will not shift into the last gear untill it hits between 4.5 to 5 thousand rpms. And if im going up a steep hill it will shift down and the rpms really rise. Did you ever figure out the problem?

I ended up selling the car for 700 dollars.
I explained the problem so he knew about.

R