Hey there - 1992 4.3w 4x4 - I think iv'e read about every thread on the net about elect. 4wd there is- typical bad tcase valve change, PO had striped out the threads the hold the valve so changed out tcase instead of heilcoilin it. no prob with swap but still no 4wd low after swap. light does the typical 30 sec blink then stays in 4wd high - both tcases act the same, I can hear the encoder motor switch gears for 2wd to 4wd - tccm does it's clicks so it's getting some signals - switch on front diff and a vacumm two wire switch on a T in the vacuum line that runs too the front diff actuator - so what my question is which switch controls the tccm and if not both of them what does the other one control