my 97 eclipse GST auto. with 118,000 miles on it won't shift to higher gear past 2nd gear. I'm going 40mph on 3000rpm. I've read some posts and some say it's the trans. or a "vacuum" line? How can I check it for myself.
I don't know that much about cars and don't want to get ripped-off. What are the indication that it's only transmission fluid, what's a "vacuum" line, and what are the indication of a greater problem.

thanks,