1997 Riviera transmission shift problems

My 1997 Riviera recently developed a trans problem in that it has what I would describe as a "hard shift" from 2nd to 3rd gear. It doesn't do it all the time and comes and goes while driving, can do it when car is cold or when it is at normal operating temp. Today I noticed that it had the hard shift even from 1st to 2nd and then 2nd to 3rd. The car has 81,000 miles on it, does anyone know if this is a transmission problem or a computer related problem?

My 1997 Riviera recently developed a trans problem in that it has what I would describe as a "hard shift" from 2nd to 3rd gear. It doesn't do it all the time and comes and goes while driving, can do it when car is cold or when it is at normal operating temp. Today I noticed that it had the hard shift even from 1st to 2nd and then 2nd to 3rd. The car has 81,000 miles on it, does anyone know if this is a transmission problem or a computer related problem?
The car should be scanned on a trans function scanner, looking for a problem with codes 1811 or 1870, both the valve body and the pcs solenoid are trouble areas.