So I have a constantly flashing 4 x 4 light on my dash. This research I have done points to "hall" sensors. I have no idea what these are. I replaced my speed sensor on the rear differential and that has made no change. What sensors are on the transfer case that can be replaced? Without looking, my research online has indicated that there is only a shift motor on the transfer case and no sensors. I have yet to change the speed sensor on the transmission. What and where are the sensors that can be replaced?