This has happened to me 2 or 3 times in the past 2 or 3 years, but it's starting to cause me some concern.
Today I was driving up a large hill and the car shifted into 3rd and I was able to maintain 65 MPH at about 3K RPMs the whole way up, no prob. But when I got to the top of the hill the car would not shift up and the RPMs would stay at 3K while going 65 on level ground. I tried slowing down by 10 MPH or so, but it wouldn't shift. Finally when I came to a stop light and then resumed back up to speed the trans acted normally. I checked the tranny fluid when I got home and it doesn't seem burnt and is a healthy reddish pinkish color at the correct level.
What would cause the car to stay stuck in 3rd like that?