In my old 94, the 4WD low input changed the shift tables, because IIRC 93-94 shifted by MPH and not RPM. Mine was actually incorrectly plugged into the EGR wiring when I bought the truck and it was all screwy. It would be fine cold and then think 4lo was engaged when the EGR warmed up to active and would shift to OD by 12mph. That took me a little while to figure out...haha