Transmission question. Car drives fine on flat city street and slight inclines.

What is your question?

On steep inclines the engine revs up, and I can only reach about 25 mph. On freeways I can only to get to 45 mph. Since these experiences I have not driven the car much and only on flat roads. Does it look like a transmission rebuild? I am going for an estimate on Monday with AAMCO. The car has 79K miles.