The front locking hubs on an F250 are there to engage four-wheel drive when you need it and disengage when you don’t. The front wheels do not have to be turned for the hubs to engage or disengage.
Locking hubs come in two varieties- automatic and manual. Automatic means the hub is engaged all the time automatically by some sort of vacuum system acting on a plunger inside the hub, while manual means you have to manually push or pull something before it will work.
Manual locking hubs must be locked by pushing or pulling on them, but vehicles equipped with automatic hubs can lock them simply by shifting into four-wheel drive. Although most vehicles built today only require the driver to shift into four-wheel drive (rather than stopping and locking hubs), there is a separate set of gears for a four-wheel drive if the driver desires to use them.
When you shift into or out of the four-wheel drive, your F250’s front end will make some noise as the hubs engage and disengage. This sound can sometimes be mistaken for a loose part, but it is nothing to worry about; the hubs are designed to make this noise under normal circumstances. If you hear a persistent clicking or popping, however, it may indicate that something is wrong with your hubs. If this happens when you try to lock your hubs they may not work properly and should be checked by an experienced mechanic as soon as possible.
Working of Front Locking Hubs
Well, there’s not much to it. Basically, the hubs are designed to lock into place whenever you engage 4 wheel drive. The actuator arms (that contain the locking pins) are spring-loaded and automatically extend out when engine power is applied, but retract inside of each axle housing when power is removed. The hubs do not turn with the steering knuckles or spindles – they stay fixed in position until the 4WD is engaged again. This allows for an open differential on both sides of the vehicle so that tire wear will be even over all four tires, rather than one tire wearing more than another because it has to take on all of the torque.
I’m not 100% certain, but it appears that one side of the hubs contains a manual locking mechanism (a button or plunger to be pressed in) while the other side is automatic. The reason for this is that I’m 99% certain that both sides are not actuated simultaneously. If they were, then there wouldn’t be much point in having them on the vehicle at all – you could just engage 4WD manually by shifting into neutral and attaching some chains directly to the tires! That’s how my old Nissan Pathfinder was set up. Also, there’s another post about “how do transfer cases work?” which states:
“When an automatic part-time system is placed in 4WD, the front and rear driveshafts turn at the same speed which means that side forces do not develop. This is why automatic 4WD systems will not damage a part-time 2WD system and do not make any difference in fuel consumption. The locking hubs of an automatic system are controlled by an electromagnetic coil inside each front or rear axle.”
So it seems that only one of the two locking pins is engaged at any time – allowing free differential action on both sides (and therefore more equal tire wear).
How to Manually Lock Hubs on F250
Before you attempt any repairs make sure all power to the vehicle has been off for at least three minutes! Also, take care in freeing up any seized bolts or moving parts. If you are not comfortable working on your vehicle then take it to a professional for repairs.
OK, now that we got the disclaimer out of the way let’s get to work! The first step is to remove the bolts located behind the hub assembly. This will allow you access to the inside of the axle where you can see and engage or disengage your hub. There are 6 bolts; one for each wheel. They should be pretty easy to spot. Next, place your truck into a four-wheel-drive high (4H) by rotating the 4WD knob located next to your steering wheel You do not need to put your key in the ignition for this step!).
Now, rotate your wheels while watching your axle. You will see one of the following happen:
1. The light on top of your truck will flash which means you are four-wheel high. At this point place, the truck back into four-wheel low (4L) by rotating your 4WD knob to the left counterclockwise until it stops then clockwise until you feel it engage.
2. After rotating both front wheels all the way clockwise or counterclockwise, if they stop before reaching a complete stop then you have not engaged either hub lock so keep trying! After making two full rotations if your wheels don’t stop both of your hubs are engaged.
3. If the light on top of your truck flashes, you only had one hub engage, or if it does not flash at all then both hub locks are engaged (figures 5a and 6) At this point rotate the wheels again; clockwise for the right lock and counterclockwise for the left lock. If they don’t disengage after making two rotations, continue rotating the wheel until they do while watching inside your axle. You may have to keep rotating in some cases up to four times but once they disengage you will see them slide back down into a position where you can pull out on them with pliers or a socket wrench if needed (Figure 7). Remember, when you disconnect your hub locks always engage both and rotate your wheels while watching the inside of your axle.
NOTE: The ABS light may come on when you change to 4L but it should turn off after a few seconds. If not, have the work done at an ASE-certified shop or Ford dealership!
Now that you are in four-wheel low (4L) go back into four-wheel high (4H) by rotating your 4WD knob counterclockwise until it stops then clockwise again until you feel it engage. At this point drive around for a little bit to check if your problem is resolved. You can also try disengaging all of the locks and engaging them one at a time while driving in 4H to see if it is any of those locks that are causing your problem. And finally, some insurance companies have a clause for locking differentials that allows you to manually engage them so keep this in mind as a last resort!
If you follow these instructions the repair should only take about 15 minutes and cost very little. However, parts can be expensive on some vehicles so always do your research before purchasing anything online or from an auto shop not located near you!