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I am new to the forum and have just obtained my first jeep since the late 1970's. I now have a 2015 Rubicon Unlimited and am still learning how it is supposed to work. I recently tested the 4WD and was surprised to find that the front differential seems to lock when either in 4 high or low. This makes it very hard to take tight turns with the front tires needing to slip through the turn. I asked the service advisor at the local jeep dealer whether or not the differential should always lock when the transmission is placed in 4WD, and they said yes. This makes no sense to me when I already have the axle lock feature that allows me to decide when I want each axle locked. Would someone please clarify for me whether or not the differential should always lock in 4WD, and if so, why even have an axle lock feature? Thanks.
 

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When you put it a n 4wd that connects your transfer case to the front wheels. Think of it as leaving the hubs locked in the old days. If You put the transfer case in 4wd the front wheels would be locked and have power. Take it out and they are free. The locking feature on your dash will lock both front axles to gather like a positrac rear diff but solid. Only works in low with the transfer case in 4wd. Might be something on jeeps website that can explain it better. Just looked there is a video on the website:)
 

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If you where on dry pavement in 4hi or 4low.. this is exactly what should happen, as there is so much traction that both tires have power(even with out the locker on).. so this causes binding. 4wheel is part not for drive pavement use. You should however be able to drive straight at slow speed and not have issue for a few feet to make sure its all working. But feel the binding when you turn as the speed between the two tires is different(shorter path for the inside tire and longer for the outer) You don't get his feeling off road as there is slippage in the surface you are on.
 

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Thanks for the response, but I'm not sure that I follow. Even with the transfer case in 4WD Hi or Lo, shouldn't the front differential allow the front wheels to turn at different speeds through a tight turn unless the axle lock feature is activated?
 

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Wouldn’t let me edit. Not on jeeps site. Search wrangler 4wd system video and pick the rock trac system explained
 

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If you where on dry pavement in 4hi or 4low.. this is exactly what should happen, as there is so much traction that both tires have power(even with out the locker on).. so this causes binding. 4wheel is part not for drive pavement use. You should however be able to drive straight at slow speed and not have issue for a few feet to make sure its all working. But feel the binding when you turn as the speed between the two tires is different(shorter path for the inside tire and longer for the outer) You don't get his feeling off road as there is slippage in the surface you are on.
This^
 

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I guess my problem is that even though I was off road I still had so much grip that the binding seemed like the front end was taking a beating. Must have great tires.
 

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Wranglers have what is known as part time four wheel drive. (Not meant to be used all the time).

As mentioned above, when turning you have your front and rear wheels turning at different speeds. When you engage the part time 4WD the transfer case locks the front and rear differentials together. The difference in speeds causes the binding.

Vehicles with full time four wheel drive can remain in 4WD all the time as they have some sort of differential action between the front and rear axles. Usually some sort of slipping clutch arrangement or fluid coupling.

This link has a more detailed explanation with diagrams: part time 4WD systems can not be used on pavement

Even off-road, the wheel speed difference can cause your front tires to 'push' and you won't always go in the direction you want in tight turns... (I don't know if you've locked your front axle yet, but then making sharp turns will get really interesting :) )
 

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Thanks for the response, but I'm not sure that I follow. Even with the transfer case in 4WD Hi or Lo, shouldn't the front differential allow the front wheels to turn at different speeds through a tight turn unless the axle lock feature is activated?

Left and right wheels should NOT lock together, but front and rear will. Having said that though, because the front and rear are locked, turning radius will be reduced.
 

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I guess my problem is that even though I was off road I still had so much grip that the binding seemed like the front end was taking a beating. Must have great tires.

There will be binding on hard turns even on slippery surfaces which is caused by the U joints. I just switched to CV joints because of that.
 

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Discussion Starter #12
I am feeling the bind in the steering wheel, sort of bucking as a wheel eventually skids to relieve the pressure. That makes me believe that the right and left front wheels are locked together as though the axle lock is on even when it's not.
 

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You should be feeling a strong bind. If you bind it up hard enough, you can damage your driveline. (This is stated in the owner's manual). It's normal.
 

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I am feeling the bind in the steering wheel, sort of bucking as a wheel eventually skids to relieve the pressure. That makes me believe that the right and left front wheels are locked together as though the axle lock is on even when it's not.

That will happen naturally in 4wd (no axle lock). Not only the left and right wheels need to turn at different speeds, but the front and rear as well on tight turns. The left and right has a differential. The front and back does not. They are directly connected so the front/rear wheels will bind/slip, bind/slip on tight turns. This is why you should never use part time 4wd on dry pavement. There is NO slippage between the front and rear wheels and it will cause damage if done too much.


If you had the front axle lock on AND 4wd you would for sure know it. Your turning radius is disastrous.
 

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Another way of looking at it, and with a picture!! :bop:

1WD means 4WD disengaged on a non-locker vehicle. Only one rear tire has power

You will have actual 2WD when 4WD is engaged, with 1 Front + 1 Rear Tire having power, spinning with the same RPMs, ie, as previously noted, no slippage. This is where the binding comes up if one of the two tires can not "slip/spin" on the surface being travelled. Turning exacerbate the binding because front tire and rear tire are trying to move at different speeds instead of the same speed. The part-time transfer case is giving 50% to the front and 50% to the rear, whereas a AWD provides more RPMs to the front wheels since the combine front tires require more RPMs then the combined rear tires.

So when engaging 4WD with open differentials, it is not locking up the front axle nor the rear axle, it is locking up the rear axle TO the front axle.

The following is what happens when in 4WD with open differentials with slick surfaces.

https://www.artofmanliness.com/articles/gearhead-101-how-part-time-four-wheel-drive-works/

The Problem of Open Differentials on 4WD Vehicles

Open differentials are great in normal driving conditions. But because of the way in which they split power between two wheels, they become a problem in low traction driving conditions. You see, instead of splitting power evenly between both wheels, an open differential distributes power across them following a path of least resistance. This is terrible for traction.

Why?

Let’s explore this on a 2WD vehicle because you’ve likely experienced it.

Let’s say you’re trying to drive your rear-driven 2WD car up your snowy driveway. The left side is covered with snow, but the right side is dry pavement. You’d think this wouldn’t be a problem because your right rear wheel has plenty of traction on the dry pavement to power the car forward. But you’d be wrong.

In a car with an open differential, your right rear wheel isn’t going to get any power. Remember, open differentials distribute power across the axle following the path of least resistance. And in this situation, the wheel with the least resistance is the wheel driving on the snow — the left wheel. So all the torque is going to be sent to your left wheel. But because there’s no traction there, it just spins and spins, while leaving your car stationary.

This same thing happens on 4WD vehicles that utilize open differentials on the front and rear axles. Let’s use the same snowy driveway scenario. You’ve got 4WD engaged so you can make it up the snowy driveway. The transfer case is sending an equal amount of power to the front and rear differentials. You think to yourself “That snow on the left side shouldn’t be a problem at all! I’ve got plenty of traction on the right side and I’ve got both right wheels moving!”

But the differentials on your 4WD are open differentials. And open differentials distribute power across the axle following the path of least resistance. The snow-covered left side has the least amount of resistance. Guess what happens?

All the power goes to the left wheels, causing them to spin in place while your right wheels just sit there like a bunch of lugs leaving your vehicle at the bottom of the driveway. Your 4WD was made impotent by your open differentials.
 

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Are you saying that your front Diff is locked? Does it lock automatically every time you put it in 4WD Hi or Low? It should not lock till in 4WD low and only then you push the button to do so.
 

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Read up on RCV axle shafts. As mentioned, a CV joint will eliminate that bind.
 

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Discussion Starter #20
It feels to me like the front differential locks when put into 4WD hi range, but I may be feeling the bind from the front axle to the back axle, not the left front to the right front. When I make a tight turn on some fairly well packed gravel, it is very obvious that every few feet one of the front tires has scuffed the ground as it slides to free up the bind.
 
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