My transmission has been devloping problems, and after letting the truck sit for a week it has gotten much worse. The truck shifts between drive and overdrive from 45 to 60. It will keep shifting back and forth about once a minute if not sooner. When in dirve the torque converter will stay locked up for about 30 seconds at a time. I have recently replaced the TPS. Any ideas? It is an ATS transmission and TC with the commander, however the comander has never worked.