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AVGeek99

AVGeek99

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Numerous members have already answered why it was hopping, normal 4WD operation. The grinding noise is the ABS (Anti-Lock Break System) solenoids working the BLD (Break Lock Differential). Even on a Rubicon, the BLD is always active unless the axles are locked. It vibrates the steering wheel and the pedals because the ABS module is under the hood right in front of the driver side dashboard.
Does this grinding noise only occur while in 4WD (hi or lo)? Is it a constant grind or does it come and go as the driveline turns?

What you describe kind of sounds like what is going on with mine. However when I was at Poison Spider the grinding was very pronounced. Yesterday, it was there but easy to miss if you weren't listening for it.
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Agree, however none of that addresses his codes and warning lights.
The warning lights have not returned since they turned off after leaving the trail in Moab. That was about 6 weeks and 1700ish miles ago. Though I've not done any off roading since. Yesterday was the first time I engaged 4WD since then. I see the fact they didn't turn on yesterday as good, but I wasn't pushing it at all. Just driving very slow on gravel, in a straight line and some tight circles, which I will avoid in the future.
 

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The warning lights have not returned since they turned off after leaving the trail in Moab. That was about 6 weeks and 1700ish miles ago. Though I've not done any off roading since. Yesterday was the first time I engaged 4WD since then. I see the fact they didn't turn on yesterday as good, but I wasn't pushing it at all. Just driving very slow on gravel, in a straight line and some tight circles, which I will avoid in the future.
You should definitely have it checked out. You didn't do anything wrong with your transfer case. Making tight circles on gravel should not cause any issues, and you shouldn't be getting any strange noises while driving in a straight line in 4wd.
 

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What about the wheel speed sensors?

From reports on this forum, those seem to commonly fail by accumulating iron shavings from the soil (they're magnetic and exposed to the elements). If one of the sensors was out or erratic, the BLD system might have been triggering, thinking that one wheel was going faster than the other (which would explain why it happened even when you were going straight). After a while of this, the computer probably declared a sensor fault and triggered the warnings (I've heard wheel speed sensor issues can cause "Service 4WD" codes but I have no personal experience). That would also explain the ABS warning light, since the ABS system relies on the wheel speed sensors.

And then during your drive home, the high speed air blew out some of the crap in the sensor, restoring the function.

Not sure this hypothesis fits all the facts, but seems like a possibility to my (admittedly ignorant) understanding of the Jeep systems.
 

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What about the wheel speed sensors?

From reports on this forum, those seem to commonly fail by accumulating iron shavings from the soil (they're magnetic and exposed to the elements). If one of the sensors was out or erratic, the BLD system might have been triggering, thinking that one wheel was going faster than the other (which would explain why it happened even when you were going straight). After a while of this, the computer probably declared a sensor fault and triggered the warnings (I've heard wheel speed sensor issues can cause "Service 4WD" codes but I have no personal experience). That would also explain the ABS warning light, since the ABS system relies on the wheel speed sensors.

And then during your drive home, the high speed air blew out some of the crap in the sensor, restoring the function.

Not sure this hypothesis fits all the facts, but seems like a possibility to my (admittedly ignorant) understanding of the Jeep systems.
I think your summation is probably what was going on. Prior to me posting this thread I wasn't even aware of the BLD. Now understanding what that does and the fact that the ABS and traction control warning lights were on I think your're exactly right.

One of the wheel speed sensors was throwing an error which in turn activated the BLD, which caused the grinding sound and a wheel to occasionally lock for a split second.

I've had no issues since so I think it's ok. I'll pay very close attention next time I go off road just to be sure.
 

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Numerous members have already answered why it was hopping, normal 4WD operation. The grinding noise is the ABS (Anti-Lock Break System) solenoids working the BLD (Break Lock Differential). Even on a Rubicon, the BLD is always active unless the axles are locked. It vibrates the steering wheel and the pedals because the ABS module is under the hood right in front of the driver side dashboard.
Occasionally my 2021 Willys Sport will make a rubbing/grinding noise, particularly when climbing with axle articulating. The noise is identical to the noise made by Hill Descent Control. It will also make the same noise when braking hard enough on dirt to skid a little.

Does this sound like the same thing to you? And is this a problem/defect or is it "normal?"
 

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Contrary to popular belief, driving in 4WD on hard surfaces will not cause damage to the driveline, prematurely wear-out tires? Yes, cause damage? No.
If it did cause damage nobody would ever be able to wheel in places like Moab.
Every Jeep I’ve taken to Moab was shifted to 4 low and had the rear locker engaged as soon as I left the pavement and stayed that way until I was off the trail.
And the traction on Moab’s slickrock is incredible, probably equal or better than asphalt
 

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Contrary to popular belief, driving in 4WD on hard surfaces will not cause damage to the driveline, prematurely wear-out tires? Yes, cause damage? No.
If it did cause damage nobody would ever be able to wheel in places like Moab.
Every Jeep I’ve taken to Moab was shifted to 4 low and had the rear locker engaged as soon as I left the pavement and stayed that way until I was off the trail.
And the traction on Moab’s slickrock is incredible, probably equal or better than asphalt
I have to concur with Vinman on this.

I have a carport along the back of my house, which has a sharp 90 degree bend into it from the end of the driveway. That driveway is often very slick in the winter, especially late in the winter, so while backing up my 96 Ram pickup into the carport, I will routinely put it into 4WD upon starting to back up into the driveway; I will also do the same when starting out on leaving the carport in the winter (which is fully half of the year here). So I am forced to make a sharp 90 degree turn in 4WD. And yes, it does bind or shudder the tires to a degree while doing this. But I've been doing it now for over 20 years, and the transfer case on that pickup is still in good working order.
 

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Occasionally my 2021 Willys Sport will make a rubbing/grinding noise, particularly when climbing with axle articulating. The noise is identical to the noise made by Hill Descent Control. It will also make the same noise when braking hard enough on dirt to skid a little.

Does this sound like the same thing to you? And is this a problem/defect or is it "normal?"
Yes. That's the BLD functioning how it should.

https://blog.stellantisnorthamerica... to controlling how,turning at the same speed.
 

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I was not aware of the BLD until you pointed it out in response to my original question. I think mine was malfunctioning a bit when I had my problems in Moab that I detailed in my original post. But none of the warning lights have returned even when wheeling so I'm pretty sure there is nothing wrong with my Jeep. At the time I thought a rock may have gotten lodged up somewhere it should't have been. My issue stopped as quickly as it started so that may be what it was.
 

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I was not aware of the BLD until you pointed it out in response to my original question. I think mine was malfunctioning a bit when I had my problems in Moab that I detailed in my original post. But none of the warning lights have returned even when wheeling so I'm pretty sure there is nothing wrong with my Jeep. At the time I thought a rock may have gotten lodged up somewhere it should't have been. My issue stopped as quickly as it started so that may be what it was.
Something messing with a speed sensor I bet.
 

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https://4wheeldriveguide.com/why-it-jerks-and-is-hard-to-turn-in-4-wheel-drive-mode/

It's normal. But you shouldn't do it. You very likely damaged something in your driveline.
You must not be a series wheeler
Also, try to avoid full lock in 4wd. At least not for prolonged periods of time
Confirmed.

I would also explore the 4wd usage section of your owners manual.
LOL, like limiting speed in 4 low to 25 MPH. What a joke, same instructions with Ruby 4:1 xfer case and the non Ruby 2.7:1
Plenty of us routinely hit 50 MPH in our Rubicons in 4 low. But then, we do full lock turns on hard rock in 4 low.

Contrary to popular belief, driving in 4WD on hard surfaces will not cause damage to the driveline, prematurely wear-out tires? Yes, cause damage? No.
If it did cause damage nobody would ever be able to wheel in places like Moab.
Or a lot of other places.

Every Jeep I’ve taken to Moab was shifted to 4 low and had the rear locker engaged as soon as I left the pavement and stayed that way until I was off the trail.
And the traction on Moab’s slickrock is incredible, probably equal or better than asphalt
I disagree with this, I don't hit the lockers until I need them or it appears I'll need them. For those who are over locker anxious, you'd be shocked what you can get through without them. On the other hand, I frequently hear on the radio "Joe, are you sure you've got your lockers on?" or my wife asking the same when I can't make it thru a line. Oops, then I crawl right through it.
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