95 Trans acting up. HELP!

my tranny started acting up the other day. i drove it to work and everything was normal. when i left it wouldnt shift out of first gear. i pulled over and checked the fluid and it was fine. i drove off and it shifted but not until about 4500 rpm. After that it shifted through gears but its not as smooth as it used to be and when slowing down the car shifts down early and i can feel it hit dropping gears. then it started to like pop out of gear or something cause it would just rev up like it was in neutral. at that point i just pulled over and had my buddy tow me home. My dad and i replaced the filter and the fluid and it still does it. anyone have an idea of what the problem could be? What really confuses me though, is that the tranny has just over 35,000 miles on it.
thanks
justin

Check the engine idle speed. If it is okay check the electrical connectors--make sure they are tight and not corroded or damaged. Inspect the shift control cable. Make sure it's properly adjusted and the linkage operates smoothly. If the above are all right take it to a transmission shop and let them diagnose it.