Say it isn't so! The transmission was serviced - drained, new filter, refilled - not long before you bought the car, and that was the 2nd transmission...
I guess it just couldn't handle the torque, it was fine up until last fall, then occasionally (going around sweeping turns, especially 895spur off of I-97 it started the torque converter issue. If I had a use for the car, I would see about getting conversion done myself, but my needs have changed so I really need a much newer vehicle. It still a nice solid car, drives nice, but the torque converter started malfunctioning daily, then last week or 2 trans slipped a little in 2-3 up shift. I towed it to Trans shop ( only because I didn't have a ride) and it slipped alot for him, when I picked it up, a couple not miles down the road, it started slipping more, I nursed it home, try to stay on i-97 to eat 50, bit hit traffic at 97-rt3 split and the halfway down 97, it wasn't wanting to up shift, I would pull over and the start over and would be able to get it to 5th.
This Fortunately, it served me well when I really needed it to, so that just life, hopefully I find a good home for it for some to convert to manual and get years of use from it