I have a 1994 extended cab silverado 1500 with a 5.7L and I believe a 4L60E trans. I was driving home and everything seemed to be working right until I came to a stop sign. Then when I took off it felt like it was either slipping or trying to take off in 2nd gear. I pulled onto the highway and it wouldn't shift into high gear so I drove the rest of the way home (about 18 miles) around 35 MPH at almost 2800 RPM parked the truck for the night. The next day drove it and everything seems to be shifting like it should. Any ideas of where or what to look for would be much appreciated.

I've owned the truck for about 10 months and have put about 8000 to 9000 miles on it with no problems and was told that the trans had been rebuilt around 15000 miles before i got it. the fluid level is correct and the fluid doesn't look or smell burnt