1992 New Yorker Transaxle Issue

I have a 1992 New Yorker with a 3.8 and only 46,000 miles on it. The transaxle will not go into gear (either forward or reverse) right away on a cold start most of the time and it will occasionally slip under load. If I give it some gas it will usually go into gear but it will be locked in 2nd until I stop and restart it, which I know is a Chrysler safety feature. I have had the fluid and filter changed twice within the past 500 miles and no garage can find any problem with the transaxle. The computer shows no codes. My question is could a bad TCM cause these symptoms or should I be looking at something else first? Could the TCM need a firmware upgrade? I think there is a TSB on this? Thanks.