No you do not need to put it in reverse. There are no locking or unlocking hubs. You need to check the vacuum lines from the solenoids on the firewall all the way down to the acuator mounted on the differential. If you have any vacuum leaks 4wd will not engage. With the right front axle not locked 4x4 will not work.. The vacuum line leading down to the acuator are blue and red...