98 Ford Ranger 4x4 Problems

My 98 Ranger will not shift into 4 wheel drive. Got flashing 4hi/4lo 6 times every couple of minutes. Disconnected battery to reset computer and no more alarms, but still won't go into 4x4. This was the only year they put vac lines to the hubs. Replaced actuator motor, but still no good. Any ideas or suggestions?
Also, where is the module located for the shifting in and out of 4x4?