OT 4x4 pulling

My 4x4 has me baffled.... It drives and tracks down the road straight, but when it's got the 4x engaged it pulls to the right. After disengaging the 4x it will continue to pull to the right until you back up a few feet. It has the factory auto/manual lock hubs and my assumption is that the backing up disengages the auto lock of the hub. The truck will drive straight with the hubs manually locked.... until you engage 4x, then it will pull right again until you disengage 4x and again back up.

The 4x seems to function normally in all aspects except for this pulling issue.

I've been through my share of 4x4 front axles from hub to hub and I can't really think of what would cause this. My only fear is that maybe the axle bearing in the r/h spindle is chewed and creating drag, but to create enough drag to make the truck pull, it would about have to be welded.

The truck is a 2011 Ford F-250 Super Duty which has a solid front axle. Any clues from the 4x front end experts out there?

1. left hand axle shaft broken.
2. right hand bearing galled and dragging.
3. right hand disk brake calipers rusted and not completly releasing after brakeing. (most likely)

I would look at the hub locking mechanism in the hub, as well as the pivots for the spindle at the Ujoint. Jim

Since you have the manual/auto hubs I assume its a F250/350 right? Anyway the auto mechanism uses vacuum and the vacuum lines going to the hubs and o-rings in the hubs are known for leaks. It sounds like the problem might be related to the LH hub not engaging.

I kinda eliminate 1 because my testing shows it has traction on
both front wheels.

On 3 it actually quits pulling right in 4x when the brakes are
applied and goes straight. It has no pull during braking 2x or
4x.

Have you jacked it up and turned everything over by hand?

There are three orings a seal and a vacuum line that engage the hubs. Unhook the LH hub vacuum line and hook a tester up to it. If you dont have a vacuum tester AutoZone loan a tool program will have one it will probably pull down some but my money is that it will bleed off as soon as you stop pumping. It is a tear down but you will most likely find the seal is bad and the hub is not engaging with vacuum.

OK, here is the CORRECT answer. The front differential is not set up correctly. Bearing preload on the carrier is too tight. When I worked in Ford dealers, I repaired MANY trucks with the same problem.
Explanation:

The front drive assembly is offset for clearance of the engine oil pan on most models. This causes a bias in weight/drag on the front drive mechanism.

When you engage the 4WD, the transfer case sends power to the front unit. This engages your "automatic" hubs. They should really be called one-way hubs. When they receive power, they lock up, but when you remove power, you have to back up to release them.

This imbalance in the location of the front differential added to carrier bearings being too tight causes pulling to one side or the other. There is enough friction in the carrier to cause a pull.

This is not easily detected by turning things by hand because when you have the wheels raised and try to turn a wheel, the side and spider gears turn instead of the carrier.

The fix is to disassemble the differential and set the side bearing preload correctly. If it is a Ford diff, it is set with outboard shims. If it is a Dana, the shims are on the inboard side of the bearings, and require removal of the bearings to replace the shims.

I can give you a procedure for measuring and setting bearing preload if need be. I have observed that quite a few of the 4X4s are set too tight right from the factory, Most will loosen up with usage, but a few are too tight to "wear in" so to speak.

My email is open if you need to discuss it further.

My vote is the needle bearing in the spindle on the right side. Jack up each side and turn the wheel with the hub both locked and free.

If it were the needle bearings it would be all the time - not just when the front end is locked in.

The post below about the differential bearings not being correctly loaded makes the most sense - especially on a Ford front end.

For some reason lots of them have limited slip front ends (as the OP says both front tires spin when locked in). An open differential probably wouldn't have this issue.

On the super duty Fords there is a needle bearing that carries the axle shaft inside the spindle. Not referring to the roller bearings outside the spindle. Also no front LSD from Ford.

Cannot put limited slip differential into a FRONT DIFFERENTIAL. Interferes with steering, and can cause loss of control. A MAJOR safety violation. NHTSA would never allow it.

Tell Ford that.

As taken from the front axel on my Ford:

Ford ID: E3TA - UC / Dana ID: 610198-11 = Dana 44 / 3.54-1 / LIMITED SLIP / Free Running Hubs / 3550 lb. Front Axle Capacity

I had a 95 150 with a limited slip in the front and it was very hard to drive straight on a snowy road. Chuck

Actually a lot of the Fords with Dana 44s in the front are LS. I believe (and I could be wrong) LS was standard on all Ford Broncos in the late 80s to 95.

I did miss the part about this being a 2011 with a solid front axel.

Ok, if this is the cause, why will it not duplicate the same symptom and pull to the right when the hubs are manually locked? Manually locking both hubs should engage both left and right axle shafts and differential carrier to turn as the truck rolls just as if it was being driven by the t-case. If anything that should create more drag than driving the axle with the t-case.

I have basically tried every variation of hub and t-case setting and driving motion to isolate the problem and it's not making any sense to me. I have yet to lift the axle off the ground and compare the amount of force required to turn one side vs the other or listen for any noises.

From your description of the problem, it appeared that you had the same type hubs that were used on any number of Ford vehicles. On the Explorer, Ranger, and Bronco II, the "automatic" hubs would engage and lock up when power was applied to the front differential. Once the 4WD was disengaged, you would have to back up about 10 to 15 feet to get the hubs released. In this type of system, most of the front drive hardware was NOT MOVING unless the 4WD was engaged.

According to the information you initially gave, and with this type of system, when in 2WD, all that is turning is the hubs, rotors, and spindle bearings. Once the 4WD is engaged, the axles and front differential turn with the wheels.

Now, logical deduction says that if the vehicle tracks properly when NOT in 4WD, but pulls to one side when 4WD is engaged, then only the actual 4-wheel-drive components are suspect. Those components that are ALWAYS turning are NOT suspect. Therefore, that leaves the axles and carrier bearings as the suspect parts. Since the axles are supported at both ends, that should eliminate them as they are not much more than a link from the differential to the hubs. This leaves the carrier bearings as the primary suspect. Also, to clarify a bit, the outer ends of the axles would become locked to the hub/spindle/bearing assembly (which is NOT suspect as it is ALWAYS turning), and therefore allows no opportunity to cause a drag at the outer end.

Keep in mind that I spent about 30 years in Ford service departments as a class A technician, and was ASE certified as a Master Auto/Heavy Duty truck technician. I encountered several vehicles that behaved as you describe. Each one was repaired by adjusting the carrier bearing preload.

NOW, if your hub setup is different than what I have described above, then the correct process of diagnosis would be to first eliminate parts that are not EXCLUSIVE to the 4WD being engaged. ONLY those parts that are used ONLY when 4WD is engaged would be suspect - according to the information that I have. AND, like a computer, if I have bad data, I would reach an incorrect conclusion. But, if what I am told is accurate, then my diagnosis should also be accurate.