The front wheels on a Ford Bronco have manually locking hubs. These hubs are designed so that if the driver wants to go into four-wheel drive mode, he just has to get out of the truck and manually lock the hubs by turning a dial. These hubs can wear down; and when they do, they won't be able to lock or unlock the hubs properly. To fix the problem, the hubs will need to be removed from the front axle for servicing.
Remove the bolts holding the hub cap to the center of the wheel with a hex head key. Take the hub off of the wheel.
Take out the snap ring located underneath the cap with a pair of snap-ring pliers.
Pull out the locking ring underneath the snap ring. Attach a hub puller to the body of the hub and remove it from the axle.
