I have a GM 440-T4 automatic transmission. Yesterday I started noticing a problem with the shift timing. The vehicle runs up to around 26mph before shifting from 1 to 2 and runs up around 48mph before shifting from 2 to 3. This problem seems to come and go. I kicked the passing gear in, and the problem seemed to clear up, it shifted normally the next time I stopped and started again. Any idea what is causing this shift timing problem? Is something getting ready to go bad? Why is the problem intermittent? Thanks in advance for any info.