HI; I have have the same problem with a 93 Aerostar 3.0. Below 42MPH Normal above 52 Normal. At 45 the converter locks up than unlocks. Over and over again. It makes no differance if the Engine or trany are hot or cold. 160000 miles never a glitch great Van. Fluid is red. Above 52 I can down shift normal. At 90 it pures like a kitten.
All this time it has worked great 3 weeks ago just like u pop a switch.
Topgo Been around along time but I don't want to tear into the Transmission if the L500 super cushion is slipping in the Radio.

PS only codes is u guested it "111"