So I believe that my 1988 Chevy 1500 pick-up possibly has a transmission problem. The other day I was driving my truck home and noticed it revved up a lot more than usual. A few days later, the truck would only go up to 30 m.p.h. and then it wouldn't go any higher and continue to just rev up. I changed the transmission fluid and that didn't help it out any. So what could the problem be?