1997 F-250 Light Duty Manual Shift 4X4 Code P1876

Getting a Code P1876 Replaced both Vacuum Solenoids on the Pass. Side and the 4wd Indicator switch on the Transfer case. Truck still will not go into 2wd. When in 2wd position the Front Drive shaft stays locked. When we switch vacuum lines at the Accumulator, the truck will go into 2wd but the light still stays on. In addition when we Manually push the ball in on the switch the system works fine. GEM Module seems to check out fine. Does anyone have any info on whats going on and what direction we can go in next? Thanks - JT