1994 GMC Sierra Not shifting

I have a 1994 GMC Sierra 1500 with an automatic transmission. It will shift from first to second, but after 2800-3000 rpms in second it seems to kick out of gear. It will not go into third. It doesn't seem to go back into gear until I come to a complete stop. Any suggestions?

I have the same type of problem right now with my 94 GMC Sierra. Had fuel pump changed a week ago. RPMs in 1st gear go over 3000 sometimes before it shifts to 2nd then acts like it isn't getting fuel again. I think it could be Transmission related like Torque Converter but I am no Trans guru.