My 1994 4WD won't go into any gear but 2 wheel high range,why?

sounds like a vac. supply issue. start eng. and unplug vac connector from transfercase. see if you have vac. to one of the ports. if not, there is your problem. If there is, reconnect hose to switch, go to ft. axle and unplug from axle motor. See if there is vac. if no, you have a split hose or clogged switch at transfercase.. If you do have vac, the problem is in ft. axle vac. motor. Could be ruptured diaphram, or the motor is froze due to rust or debris. Or sliding collar in ft. axle is stuck. Hope this helps.....

Just fixed mine. The vaccum line was loose in the fitting that goes to the front axel. So be sure to check and press all vaccum lines into fittings before replacing the vaccum motor.