What's wrong with my car?!?!?

The other day when I was driving my car, it started up just fine. But then when I tried to press on the gas my RPM's went way up but I wouldn't go more than 40 mph. Is that my transmission going out or did I just get bad gas? I put some chemtool (I think that's what it's called) and it has be doing fine. If it is my transmission, should I get it rebuilt or should I just buy a new one? What's the best thing to do? My car is a 1993 Chevy Cavalier z24 and it has just over 143,000 miles on it. Thanks!!

auto/manual?

assuming its an automatic, does it just stay in the same gear for way longer then its supposed to, and revs almost to the redline before shifting?????

It is an automatic and it usually would rev up to between 3 and 4 or 4 and 5 rpms. It wouldn't ever go over 5. Is that the red line??

It is an automatic and it usually would rev up to between 3 and 4 or 4 and 5 rpms. It wouldn't ever go over 5. Is that the red line??
If it keeps on doing just take it to a tranny place, but it is most like the clutches in the automatic are going oue that is when you rebuild it.

if its like the problem i described, it could be something as simple and cheap as the throttle pressure cable