Automatic Locking Hubs

Figure 11:

In the manual hub, locking occurred when the locking knob was turned by hand. In the automatic hub, it is front axle shaft rotation that locks the hub. As long as the vehicle is in 2WD, the front wheels turn freely on the front axle. However, when the vehicle is shifted into 4WD, the front axle shafts begin to rotate. This rotation actuates a cam that moves the locking gear into locked position (Figure 11).

NOTE: THE INTRODUCTION OF CHAIN DRIVE MADE IT POSSIBLE TO INSTALL AN ELECTRIC MAGNET CLUTCH TO SPIN UP THE FRONT END COMPONENTS AND AUTOMATICALLY ACTIVATE THE LOCKING HUBS. THIS, IN TURN, MADE FORD "TOUCH DRIVE" (ELECTRICALLY CONTROLLED SHIFT-ON-THE-FLY) POSSIBLE.

Automatic Locking - Manual Shift Transfer Case

In order to initially activate automatic locking hubs in a vehicle with a manual shift transfer case, the vehicle is stopped, the transfer case lever is moved to 4H and the vehicle is ready to drive. In order to select 4L, if the vehicle has an automatic transmission, the transmission must be in NEUTRAL, not PARK, before making the shift.


The hubs will automatically lock when the vehicle begins moving again. After this initial shift with the vehicle stationary, the transfer case may be shifted back and forth between 2H and 4H while the vehicle is moving, as long as the hubs remain locked. To shift in and out of 4L, the vehicle must always be stopped.

Unlocking Automatic Hubs - Manual Shift Transfer Case

To unlock automatic hubs with a manual shift transfer case, the operator shifts to 2H, stops the vehicle and reverses direction for a minimum of 10 feet in a straight line. If the vehicle was going forward, driving in reverse will unlock the hubs. If the vehicle was driving in reverse already, driving forward will unlock the hubs.

What actually unlocks the hub from the axle is the release of the cam (see Figure 11). This occurs because the axle shaft is no longer driven by the transfer case and when the hub cam rotates back to the disengaged position, the shaft is disengaged from the wheel and no longer rotates.

However, this all assumes that the transfer case has actually shifted. What if, for some reason, such as driveline windup, it hasn't? In that case, as soon as the vehicle moves forward (or backward) again, the front axle rotation will continue, the cam will ramp up again and the hubs will remain locked. 4WD owners may complain about this happening. If they do, it may simply be that they didn't get the torsional windup out of the system before shifting, or it may be an indication of the failure of a component in the transfer case or the hubs themselves.