[djd99]

I've had 2 vehicles do this very same thing to me. One was a 97 s10 4x4 with 150,000.. The problem with that truck was it shifted fine for about 15 minutes of driving then it would start to shift real hard.. Pull over let it cool and it would be fine until it heated up again. Second was a 98 S10 blazer with 80,000 miles on it and that truck would slam in second and third gear all the time. I had replaced the valve body on both trucks(Myself) and that fixed both problems. Now even if they rebuilt your transmission without rebuilding your valve body you would end up with the same problem. If this was me I would replace the valve body and put in a new trans filter and fluid. Good Luck