I'm by no means a mechanic, so I'll put things as best I can.
I have an 83 GLX convertible with the 3.8 V-6 and an automatic transmission. Recently, I have noticed that when I drive, mostly during a start or when I slow down, that the transmission will slip out of gear. It only happens in first and reverse, and it has gotten noticeably worse in the past few days.
Any idea what may be causing this? I put a new tranny in about 3.5 years ago.

Thanks in advance for your help!