I found out my 96 s-10 blazer wouldn't shift into 4 wheel drive by getting stuck in a river bed, I replaced the actuator because the diaphragm was ruptured. the next time it didn't work I assumed the same thing happened, but when I checked, it was full of transmission fluid. If I understand correctly, the transfer case has an electric shift motor, so where is the fluid coming from? is the vacuum line tied into the down shift actuator on the transmission and that component have a ruptured diaphragm?
check your actuator switch located on the transfer case. it has three vacuum lines running to it . one line is always vacuum. one is the exit to the actuator and the other is a vent line. The switch has a little ball on it and it gets stuck in the open position as it goes bad. this can cause fluid to flow to and through your lines. replace the switch its 20 bucks and blow out all your lines with air or replace the lines.
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