OSCILLATING HUMMING NOISE/VIBRATION AT HIGHWAY SPEEDS, GOES AWAY IN 4H

[jakemyers24]

Imo I would self diagnose, going as far as disconnecting the pig tail connection for the actuator, before bringing it in. You really need to pin point it for the techs on this one

Any advice on how to disconnect the pigtail? I’ve pulled back the little red tab on the top but for the life of me, I can’t get the plug to disconnect. Thanks!

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[andersman02]

Any advice on how to disconnect the pigtail? I’ve pulled back the little red tab on the top but for the life of me, I can’t get the plug to disconnect. Thanks!

Can't help ya there, I swapped broncos just before I was at this point. Went through all the dealer BS. Swapped my front diff fluid and it was filthy and fair amount of metal. Pretty sure the next time I would have brought it in, with a pin point and fluid example, I would have gotten a new front diff

 

[andersman02]

Just got my 22’ outer banks back from the dealer. They found the noise and recognized that it exists, but they won’t work on it because of the lift, tires and exhaust. What’s even weirder is they ansvised me before I dropped it off that if the repair wasn’t covered under warranty that I’d be charged an $170 inspection fee. Well they didn’t charge me, which I thought was odd. Seems like they just don’t want to do the work. Any advice? Try a different dealership? Or just trade it in? I’m so pissed off.

I hate to be that guy, but you lifted and put bigger tires on. They absolutely could refuse warranty work because of this. Bigger/heavier tires= more stress on the driveline.

I'd try another dealer but don't be surprised

 

[adamb004]

My girlfriend doesn't notice that her suspension in her car is totally whopped out, and she doesn't notice that the inside of her windshield is so filthy that there is a permanent haze, and the other day while riding in my bronco she asked what that noise was.... so, yes, a non-enthusiast would notice when it's at its extreme.

As for the description, the noise isn't usually constant, it's like driving over evenly spaced sets of rumble strips, and it doesn't change the volume or intensity as I speed up or slow down or push the clutch in or anything.

I do not understand how the front diff works because I haven't seen it and I haven't taken it apart. But if I had to isolate potential causes I'd narrow it down to whatever mechanism engages/disengages the front axles, or the CV joint. Either the front axle isn't being completely disengaged, or the CV joint is failing (or some combination of both). I will qualify my mechanical skills this way: When my dad's race team was racing, the first time we finished the 24 hours of Daytona happened to be the year that our mechanic had a heart attack and one other guy and I put the car together. I'm not saying I'm mechanically gifted or even that knowledgeable, but I'm not a total moron. Ok well actually sometimes I am a moron, but still, there is only so much that can cause this issue. The fact that a couple people have experienced the same thing is comforting, though.

Did you send up finding out what was causing the issues? I am having the exact same on my 22 big bend. Had the wheel hub replaced and it is still making the vibration/humming noise. Now at a different dealership and told them to check the front axel disconnect, hoping that is the solve.

 

[adamb004]

Has anyone found the official solve to this? 22 big bend with 42k miles and have been experiencing the same issues everyone’s mentioned for the last 2 months. Dealer refuses to consider the possibility of it being the FAD unfortunately and says it’s due to my wheel/tire setup.

 

[PickleRick93]

I was assuming i was having wheel bearing issues. My oscillating hum became a constant hum on the freeway one morning and told the dealership i was assuming it was the wheel bearing. They swapped it out under warrant and sent me on my way. I have no idea if they actually examined the wheel bearing. I wish i had asked to see it.

A few weeks later the issue reappears only when its cold/below freezing and does so randomly. It hasn't been constant this time. It usually goes away when I come to a complete stop then accelerate again. Humm for a second, stop for a second. repeat. you cant hear it with the windows down.

Going to go to the dealership and explain that i suspect its the 4wd actuator. The issue will not consistently show its self and cold weather is about gone until next fall so I'm betting the dealership isnt going to change a part on a hunch.

 

[jresler22]

I'm fairly certain my 2022 Big Bend just started having this issue the other day. What doesn't make any sense is if it is related to the FAD then why would it start randomly one day that I was driving around in 2H all day.

Also, of course I just recently did a 2in lift and put 35s on, and then the issue starts. I think that is just some really bad timing as I've had them on for all of about 500 miles, and I do not see how the larger rotational mass could have any impact on the front axle disconnect especially in that short of time.

Has anyone actually had this issue repaired and gotten an explanation of what the actual failure was?

I guess my next step is going to be to drain the front differential and look for any excessive metal in the fluid and see if there is any obvious issues. My other thought was to throw a camera underneath and record the front drive shaft, as if the FAD is not full disengaged for some reason I should see the front drive shaft start to spin up.

My plan was eventually to replace the front FDU and the rear axle anyways but looks like that might happen sooner than I was planning. Ford and their nonsense with this stupid FAD and welded rear axle ring gear is driving me nuts.

 

[jresler22]

Well took it into the dealer and they ended up replaced the FAD portion of the front axle assembly (under powertrain warranty), as it appears to be available separately now. https://ford.oempartsonline.com/oem-parts/ford-axle-tube-mb3z3d102b

Though I just went to pick it up and instantly noticed the issue is still present. So now I had to take the tech for a drive and show him, which he agreed it was still making the noise. So, I'm back in a loaner car waiting for them to come back with their next step for repairs.

I will make sure to post any updates as I still have never seen an exact explanation of the root cause of this issue. I know for some people it sounds like replacing the complete Front axle assembly resolved their issues, but then I've seen some comments of people saying it didn't so who knows.

 

[jresler22]

So, the dealer did end up finally just replacing the whole front differential unit along with the driver side half shaft to resolve the issue.

The communication wasn't the best as the initial repair the service adviser said that was being done was the whole FDU, but that was not the case as they attempted to just replace the front axle disconnect actuator that I referenced in my last post. They replaced that and said it was good to go but it in fact was not. I picked it up and instantly the noise was still there, so I turned back around and took it right back.

That's when I went for a ride with the tech to make sure he still heard it and he agreed it was still making noise and that's when they ended up deciding to replace the whole FDU. I was not able to get good info from the dealer for an explanation on what the exact failure was. That is still a bit of a head scratcher for me since if you unplugged the front axle disconnect actuator the issue went away, but replacing it did not resolve the issue. Which means something in the FDU was also part of the problem causing the noise/vibration.

Now I'm just hoping the next front axle unit lasts longer than 45k miles that the original one made it, as next time It will be out of warranty more than likely. Also, just to clarify they did replace everything under warranty so that was plus at least. That was even with the old man emu lift and when I took it in I had put the 32in Badlands takeoff wheel/tires back on it.

 

[Lyssa]

Just got a new Big Bend 4 door 2026 2 weeks ago and I have the same problem. So I guess they didn't fix the issue. I have an appointment next week to have it checked.

 

[andersman02]

Just got a new Big Bend 4 door 2026 2 weeks ago and I have the same problem. So I guess they didn't fix the issue. I have an appointment next week to have it checked.

If it is the same exact sound, and it's the FAD unit, is hop under and disconnect it and see if it fixes it. If it does I'm fairly certain it's the FAD.

Also give them the link to this thread of they give you trouble.

This is a pretty difficult problem to find, specifically cause the person doing the ride along hasn't driven your vehicle for as long as you have, so it's a hard sound to hear specifically if it's not super loud in your case

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