4A acting like 4H, binding while turning on dry pavement

[Lil Red Broncette]

MY22, 2 door, 2.3L, manual, squach, advanced 4x4

Any anybody know how 4A might suddenly act like 4H binding on dry pavement? And then fix itself after using 2H several days. I had been in 4A for months and hadn't switched modes anytime around when this started. Is this something that software sets up every time I start the car in which a software glitch puts it in the wrong mode? Is this a simple solenoid that is activated that makes 4H different than 4A?

Additional detail:

I been driving in 4A for the last several months with no issues. Last week I noticed it binding, stiff turning and moving when taking the sharp turn into the garage. I switched to 2H and got the sound of the tension unwinding. In 2H I backed out and drove without issue. I put it back into 4A and headed back to the garage. Once again I experienced the binding when taking the turn. Switching to 2H and again the tension was released. I then put it back in 4A, backed out and experienced the same binding backing out which makes sense since it was the same tight turn but in reverse after I released the tension. Once again switched to 2H to release tension.

To confirm it was the same as 4H I performed the same sort of experiment in 4H and got the same binding. So I put it in 2H and parked it overnight.

In the morning I put it back into 4A and it exhibited the same issue. I put it in 4H and went to work. After work I put it in 4A and experimented in the parking lot at work turning tightly and had the same issue.

I made an appointment with the dealer which is later this week. I continued to drive it in 2H. Yesterday I decided to see if it was still exhibiting the issue and put it in 4A. Of course it is no longer occurring.

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[Thatguylegit69]

[/QUOTE]

In the morning I put it back into 4A and it exhibited the same issue. I put it in 4H and went to work. After work I put it in 4A and experimented in the parking lot at work turning tightly and had the same issue.

To clarify, you're saying you engaged 4H and drove to work?

 

[BroncoChallenger]

Unless I needed it I wouldn't run around all the time in 4A or 4H, especially not on dry roads. There's no reason to.

 

[MayhemMike]

Several years ago I had the windshield recall completed at a dealer. On the way home ( about 15 miles) I was contently driving when I reached a side road roundabout. As I entered the roundabout I heard the “ noise”. It was then that I realized during the recall work the tech had activated the locker hero switch. I never even noticed the switch being illuminated. Stopped and deactivated the locker and issue resolved.

 

[VirginiaHeritage]

As MayhemMike mentioned, lockers can obviously cause binding too, but my understanding is that switching to 2H won’t disengage the rear locker if it’s on, and the front locker should only work in 4L. So a locker issue doesn’t seem to match your description.

After driving in 4A on dry pavement all that time and having issues now, it’s probably a good idea to get your transfer case fluid changed, at minimum. Some would say to have the old fluid examined.

Also find some dirt to drive in and verify 4H still works.

 

[Oldhippie]

I have never had a clear detailed explanation of how 4A/4wd work but 4A definitely is tied to traction control and wheel sensors through computers…I would think “faults“ would default to 2wd/open but it may default to 4wd/lock??? clearly you have some kind of “event” going on in the 4A system…keep it 2H on pavement until it is fixed…good luck

 

[5GENIDN]

I have never had a clear detailed explanation of how 4A/4wd work but 4A definitely is tied to traction control and wheel sensors through computers…I would think “faults“ would default to 2wd/open but it may default to 4wd/lock??? clearly you have some kind of “event” going on in the 4A system…keep it 2H on pavement until it is fixed…good luck

with 4A your "advanced" transfer case works like a differential... It uses clutch packs to be able to differentiate power transfer between the front and rear.

with 4H your transfer case sends 50% of the power to the front and 50% of the power to the rear as if it were "locked"....

 

[Oldhippie]

with 4A your "advanced" transfer case works like a differential... It uses clutch packs to be able to differentiate power transfer between the front and rear.

with 4H your transfer case sends 50% of the power to the front and 50% of the power to the rear as if it were "locked"....

yeah, but how does it “differentiate”? is there actually a “locking device“ to lock it in 4H/4L? is there hydraulic pressure on the clutches? or is really just a gussied up old style “limited slip”?

 

[SamIAm66]

Unless I needed it I wouldn't run around all the time in 4A or 4H, especially not on dry roads. There's no reason to.

So then you have to ask why does Sport mode default to 4A??

 

[BroncoChallenger]

yeah, but how does it “differentiate”? is there actually a “locking device“ to lock it in 4H/4L? is there hydraulic pressure on the clutches? or is really just a gussied up old style “limited slip”?

It in effect 'locks' the clutches in the t-case to make it act like a standard t-case when you select 4H/4L. In 4A they remain dynamic.

 

[PowerBronco]

yeah, but how does it “differentiate”? is there actually a “locking device“ to lock it in 4H/4L? is there hydraulic pressure on the clutches? or is really just a gussied up old style “limited slip”?

with 4A your "advanced" transfer case works like a differential... It uses clutch packs to be able to differentiate power transfer between the front and rear.

with 4H your transfer case sends 50% of the power to the front and 50% of the power to the rear as if it were "locked"....

All the questions on how the transfer case works are in this thread.
Transfer Case Technical Discussion | Bronco6G - 2021+ Ford Bronco & Bronco Raptor Forum, News, Blog & Owners Community

 

[5GENIDN]

yeah, but how does it “differentiate”? is there actually a “locking device“ to lock it in 4H/4L? is there hydraulic pressure on the clutches? or is really just a gussied up old style “limited slip”?

I have not cracked into one of the new transfer cases, but I think 4H simply squeezes the clutches tight. 4A uses a computer to increase/decrease the pressure on the clutches.

 

[BroncoChallenger]

So then you have to ask why does Sport mode default to 4A??

Because they presume when you're in Sport mode you're going to be doing aggressive things where having added traction/drive with the front wheels would be helpful. Dry pavement isn't really that case, and even when I DO put our Bronco (or the wife's expedition, for that matter) in Sport mode, I manually switch it back OUT of 4A...because I am generally trying to get into traffic on a crowded road, not dealing with a slick surface.

Don't get me wrong, I LOVE 4A and sometimes wish my truck had it...but I still don't personally feel it is meant for dry pavement.

 

[5GENIDN]

yeah, but how does it “differentiate”? is there actually a “locking device“ to lock it in 4H/4L? is there hydraulic pressure on the clutches? or is really just a gussied up old style “limited slip”?

It is a ball ramp that is applying pressure the way I understand it... and yes the ball ramp would have to be hydraulic pressure operated.

 

[5GENIDN]

All the questions on how the transfer case works are in this thread.
Transfer Case Technical Discussion | Bronco6G - 2021+ Ford Bronco & Bronco Raptor Forum, News, Blog & Owners Community

That was a good discussion. Lots of detail. It would still be nice to crack one open and "see" how the hydraulic pressure is applied to the ball ramp... Would love to "see" the code that is involved as well. But got to admit it is a little lower on my priority list of all the things I need/want to do.

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