4 wheel high vibration

[710-oil-614]

4A is either 2H or 4H. It just automatically switches between the two based on slip conditions.

So if driving in the snow it probably detects enough slip that it would be 4H most of the time.

Think of 4A as good for greasy conditions where you may unexpectedly lose front end grip; you'd be driving along in 2H - front end starts to slip, boom, you've got 4WD

This is very incorrect.

4A is not just 2H and 4H. 4A has the ability to send a variable % of torque to the front wheels - where as 4H does not.

4A in Fords use some sorcery - but the gist of it is that AdvanceTrac uses a gyroscope that is taking measurements 150 times a second to detect things like wheel slippage, steering and braking input to slow and stabilize the vehicle. AdvanceTrac is standard on all Broncos

But that input for 4A is sent continuously and the hydraulic clutch in your transfer case will adjust the % of torque sent to the front wheels as needed.

Like others have stated when cruising or decelerating the front wheels are not receiving torque.

4A is so much more than just the combo of 2H/4H. It is an extremely valuable addition to the Bronco.

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[BrentC]

Seems to be a lot of misinformation and opinions in this thread on how 4WD systems work in general, and how they work on the Bronco specifically.

If you’ve never owned a 4WD before you will feel a slight vibration when the transfer case is putting power to both driveshafts, compared to running the rears only in 2WD (note - REAR wheels only in normal driving mode, not the front wheels). I can always feel the entire drivetrain working as opposed to just the rears in every 4WD pickup I’ve owned, and it’s the same with the Bronco.

If you are locked in 4H and running on dry pavement for extended periods, you will experience drivetrain windup. This is not good for your drivetrain and the tightness in your steering is the warning signal to switch out of 4H ASAP. Other conditions will also cause drivetrain windup and it’s good to read articles on the subject.

4A as has been stated earlier uses a clutch drive between front and rear and should modulate power to the front when slippage is detected. It works very well in my 2019 F150 though I haven’t tested it enough in my Bronco to comment. From what is said above it may not be calibrated properly and defaults to a 50/50 distribution all the time. This is worth investigating and if an update is required it should show up in a service bulletin.

The electronically-controlled powertrain incorporates a large number of electro-mechanical components so there is plenty of places where a slight issue could compound consequences. The first thing to do is determine whether a problem exists, then isolate the problem and fix it.

 

[BrentC]

This is very incorrect.

4A is not just 2H and 4H. 4A has the ability to send a variable % of torque to the front wheels - where as 4H does not.

4A in Fords use some sorcery - but the gist of it is that AdvanceTrac uses a gyroscope that is taking measurements 150 times a second to detect things like wheel slippage, steering and braking input to slow and stabilize the vehicle. AdvanceTrac is standard all on Broncos

But that input for 4A is sent continuously and the hydraulic clutch in your transfer case will adjust the % of torque sent to the front wheels as needed.

Like others have stated when cruising or decelerating the front wheels are not receiving torque.

4A is so much more than just the combo of 2H/4H. It is an extremely valuable addition to the Bronco.

Well stated, and on point. Thanks

 

[WuNgUn]

Gawd dammit! So on my way home from work, I toes it into 4A, and sure enough I can hear something AND definitely feel vibrations in the floor
Wtf
Wish I never came across this thread.

 

[NotApplicable]

I feel/hear a little something-something when in 4A, particularly at lower speeds. I can feel it under my feet in the front, whereas I never get that sensation in 2H. However, once I get above... maybe 40mph, I don't notice it anymore. Maybe its because of other road noise/vibration at that speed, or maybe it actually calms down at that point. Every time I've looked at the power distribution screen while in 4A, it always shows at least one "bar" of power going to the front wheels; I've never caught it claiming that it was _only_ driving the rear wheels. But, I don't watch it like a hawk either. I just know that I've looked at it when there was definitely no slip and I was not accelerating (or wasn't accelerating heavily), and it's always showed power going to the front wheels.

It's never been significant enough that I thought something was wrong; I assumed it had to do with parts of the drivetrain being engaged that obviously aren't during 2H driving.

I'm going to lose some cred by saying this, but I haven't actually driven it in 4H/L yet as I haven't done any activities yet that merited it. So, I can't compare it to 4H/L.

In any case, it doesn't strike me on its face to be strange that an observant driver would be able to "feel" when the vehicle is in 4A vs 2H...

 

[BrentC]

Anyone else notice any vibrations when they use 4 wheel high or 4A. Since the snow I haven’t used 4 high or 4A till last night on the interstate and I noticed right away it has some vibrations. When you let off the throttle they go away it’s only when your on the throttle. When I reached my destination I reached up under the front and felt the bottom of the front diff through that little opening and it wasn’t warm at all. First I thought it might of been the ring and pinion not properly meshed right. Thinking now it could be the front driveshaft being out of balance. Something making it not feel right.

Also I think 4A is just marketing BS because it’s just 4 wheel high there doesn’t seem any difference between 4high and 4 auto.

Ok, so I monitored the power distribution screen while in 4A on icy roads last night, and I noticed the same thing as the OP. The graphic only showed equal power going front and back (like in 4H) and I could feel the load on the front drivetrain. This is not how the system is supposed to work, if my F150 is a benchmark comparison. I reported the issue to my dealer today and I’ll let you know the response.

Also, our daughter rode in the back seat on a 2-hour, -23C trip and she froze. I could not feel any heat going under the seat to the rear. I also reported this as I understood there should be a floor vent under the front seats supplying air to the back. It was dark last night when we switched to the F150 for the last of the trip so I didn’t take time to examine the heat issue. Anyone else have heating issues with the rear?

BTW, we were baking in the front so the heat was working fine.

<edit> https://www.bronco6g.com/forum/members/21911/ FYI. Please note the following replies - others are having similar issues.

 

[Frankie945]

Ok, so I monitored the power distribution screen while in 4A on icy roads last night, and I noticed the same thing as the OP. The graphic only showed equal power going front and back (like in 4H) and I could feel the load on the front drivetrain. This is not how the system is supposed to work, if my F150 is a benchmark comparison. I reported the issue to my dealer today and I’ll let you know the response.

Also, our daughter rode in the back seat on a 2-hour, -23C trip and she froze. I could not feel any heat going under the seat to the rear. I also reported this as I understood there should be a floor vent under the front seats supplying air to the back. It was dark last night when we switched to the F150 for the last of the trip so I didn’t take time to examine the heat issue. Anyone else have heating issues with the rear?

BTW, we were baking in the front so the heat was working fine.

Funny you mention the heat in the back. I also checked mine just by placing my hand under the seats with the heat on high on the floor setting and I didn’t feel anything. I did from the front so at the time I thought I’m just not reaching far enough or missing the vent with my hand.

 

[VonMussa]

I’ve also noticed a hum. More auditory than vibratory when in 4H.

Also +1 on no flow from the under seat vents.

 

[internationlriders]

So I noticed the very very slight vibration as well so seeing this thread caught my interest as well as seeing my fellow Calgarian on this thread.

I thought when it 4A I was also seeing only equal power distribution but today on the highway out in Waiporous I saw it does in fact only put power to the rear wheels sometimes.

Also I'm 100% sure this is just from 4wd being engaged. My old Jeep did the exact same thing as well but with a bit more vibration of course

 

[MillerAndCheeto]

Ok, so I monitored the power distribution screen while in 4A on icy roads last night, and I noticed the same thing as the OP. The graphic only showed equal power going front and back (like in 4H) and I could feel the load on the front drivetrain. This is not how the system is supposed to work, if my F150 is a benchmark comparison. I reported the issue to my dealer today and I’ll let you know the response.

Also, our daughter rode in the back seat on a 2-hour, -23C trip and she froze. I could not feel any heat going under the seat to the rear. I also reported this as I understood there should be a floor vent under the front seats supplying air to the back. It was dark last night when we switched to the F150 for the last of the trip so I didn’t take time to examine the heat issue. Anyone else have heating issues with the rear?

BTW, we were baking in the front so the heat was working fine.

My Chevy had no rear vents. You had to aim the center vents to the back to get good warm air to the rear. Likely same solution with the Bronco.

 

[etmccaus86]

Yes...until 4WP gives us some more information on those locking/free wheeling hubs...

ah, yes; the ones they refuse to acknowledge are actually installed on their concept vehicle...

 

[Dubsesd]

Any update on this? Anyone bring it to the dealer? Mine is doing exact same thing and the dealer "couldn't replicate" the concern. Just wondering if anyone brought to the dealer and they had a diagnosis for it. I dont think its normal.

 

[skithebadlands]

I have a manual transmission Badlands with 9800 miles on it. I just noticed for the first time this week the exact same thing, strong vibration, not subtle (even my kids noticed it in the passenger seat), only in 4A and most prominent upon acceleration. It definitely was not there before. I can't notice it in 4L/4H. It is completely absent in 2A. I made an appointment right away and it's at the dealer as we speak. This is the first 'issue' I've had in my 11 wonderful months owning this vehicle. Done a good amount of off roading and snow driving and not one issue until now. Will let you know what dealer finds out.

 

[skithebadlands]

Dealer told me axle was damaged, they are replacing it. Don't know more yet, was it a manufacturing defect, wear and tear or what. I have done any high stress off roading, nothing like Offroadeo in Texas which I attended and undercarriage has never been hit so not sure what's up. Will let everyone know when I get more info from the dealer.

 

[skithebadlands]

From the dealer: "Something hit the axle and ripped the boot off which caused the damage. We cannot tell what it is. Part will be in tomorrow and replaced."

Maybe I should invest in undercarriage protection?

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