no kickdown under 50 mph

[Roadmonster]

Hello all again,

I bought this old 95 Roadmaster with 139k off the back row of a car lot because it was cheap and I'd always been interested in them. It had been sitting for about 2 years, but started right up. It runs and shifts okay, but sometimes the first shift is a little abrupt. I've noticed that there's no way to make it downshift from 2nd to 1st by stepping down on the pedal. After some research, I thought this might be caused by the TPS. I replaced that today and nothing has changed. I haven't inspected the transmission connections, but do know that it will downshift at speeds over 50mph on the highway. Any ideas what I should check next?

Thanks!