Got 2- inch’s of snow today and took the truck out to see how the 4wd did. 4wd works but every time I turn right or left the truck grabs like it’s in 4wd on dry pavement. Is this normal? Hubs were unlocked. Still think it’s dumb they don’t have auto locking hubs.

 

Your hubs are set to AUTO?

 

Yes set to auto. Sorry thought it was lock and unlock. Not lock and auto, but yes they are set to auto.

 

Your hubs are locking, that's why you get the binding when turning tight. It's working as it is supposed too. A smaller CV joint in a half ton doesn't do this but in a big truck with a u-joint it does.

 

Ok thank you. This is my first Ford came from a Chevy lbz and never had this problem. Maybe the ifs is the difference here.

 

CV joint versus a u-joint. Vacuum auto hub vs electric. IFS vs solid front axle.

 

Chevy deserves their reputation for providing a car-like ride.

 

No...no...NO! That's not why. Any truck with "Part-time" 4x4 which is what ALL heavy duty trucks have...brand irrespective...cannot compensate for the differences in wheel speed between front and rear axles while 4x4 high or low is engaged.

You'll note your truck has a front differential and rear differential. The reason it is called a "differential" is because it is the device which allows for the 'differential' in speeds between wheels.

If you drive in fresh snow and make a turn, get out and look at your tire tracks. You'll notice they don't all follow each other. The outer wheels actually have to travel further than the inner wheels. For this, the front and rear differential compensate for the difference in wheel speed (and hence distance traveled) *across* the front or rear axle. But notice that there are more than just two distinct tire marks in the snow...there are at least three and sometimes four distinct paths. That means the rear wheels "together" are not traveling the same distance as the front wheels "together."

Vehicles with an AWD system or 'full time' or 'permanent' 4x4 have a third, "center" differential which compensates for the difference in speeds *between* front and rear axles. Vehicles like a heavy-duty truck, and most half-tons, have part-time 4x4 without this extra differential (or clutch).

It does not matter if you have independent suspension or a solid axle, CV joints or u-joints. None of those features allow any slippage in the drivetrain. Locking hubs has nothing to do with it either. When Ford hubs are "locked" or in "auto" there is no difference, and they have absolutely zero advantage in traction over a similar GM or RAM truck. "Locking hubs" just means that when the hubs are unlocked, no power is transmitted to (or from) either the left or right front wheel. GM and RAM use something called a Center Axle Disconnect which unlocks one side...usually the passenger side...from the front differential. This method is simpler, usually run by electricity rather than vacuum, but might use a tiny amount of additional fuel when 4x4 is not in use.

What you are feeling is typical binding of a part-time 4x4 system. With only a couple of inches, the snow may not have provided enough "slip" for the tires to spin in order to match the speeds between the axles. Your tires likely were gripping the more tractive surface below. Even in fully snowy conditions, tight turns can elicit some binding from the system.

Wheelbase has a lot to do with how you feel the binding. Shorter wheelbase trucks have less difference in wheelspeed between front and rear axles, because the rear axle more closely tracks the front axle. This results in less binding. Many times, a half-ton truck is on a shorter wheelbase than an HD truck. Weight and weight distribution can also be a factor. A heavier truck may feel more binding. When I mount my 800# snowplow on the front of my Super Duty with no weight in the back, there is almost no binding in 4x4...because the rear tires have unloaded and slip easily.

Have an assistant pull your truck forward or back at slow speed, on snow or sand, in 4x4 high or low, while turning. You will see a wheel suddenly spin faster than the others. That would be a binding wheel "catching up." This is normal behavior for all part-time 4x4 vehicles. It is not necessarily the front wheel, either. It will be whatever wheel has the least traction.

Hope that helps.

 

Don't you still have to back up 20ft or so to unlock the hubs when in auto?

 

You didn't happen to accidentally lock the rear differential when you when you turned the 4wd switch, did you?

 

Not really. That method was in the old days of manual hubs and manual shift 4x4...sometimes the vehicle wouldn't want to "come out" of 4x4. Backing up would help relieve drivetrain stress from binding. The hub system uses a reduction in vacuum to unlock the hubs. Some vacuum is required to unlock them, and peak vacuum is produced in an engine while it is at idle. Diesel engines use a vacuum pump. There is typically a delay between the driver selecting 2WD on the **** and the hubs actually unlocking...but it really doesn't matter because the transfer case disconnects almost immediately. For 2017, the transfer case uses a clutch which smooths engagement and disengagements, but still mechanically locks using a collar.

 

Good point. If he has the e-locker, engaging it would definitely cause binding.

 

Being that it's on the same switch, I could see that happening.

A friend that I work with, a day or so a week, has a 2016 F250 with the electrically actuated 4wd...his first with this feature. On the way to a job one day he commented that his truck must not have a locking diff. I showed him that it did...on the same switch as his 4wd. He had the truck thru one winter w/o realizing this.

 

Ha...locking diff was a pretty important feature for me. Short of the PowerWagon, RAM offers nothing like this and GM offers the less-nice auto-locking G80 rear end.

Despite it being "so important" to me, I rarely use it. Without weight in the bed, I find traction control works nearly as well. But in the few times I have used it, you can definitely increase your binding.

I wish the locker switch was more like my Raptor's, which has an indicator if the diff is actually locked, in addition to the lock symbol being lit at night:

 

The E-locker was important to me too. Now I much prefer the limited slip. You can't beat the E-locker for positive, no holds barred traction when it is engaged. But when it isn't, all you've got is an open differential, whereas the limited slip is always on duty and directs power to the wheel with the most traction quite smoothly.