How does the 4A work?

[HeliPilot]

SAS 4 door here. No added lift. Mine has a noticeable vibration and sound in 4A that is non existent in 2H. I think you’ve been experiencing normal Ops condition.

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[TX-Hans]

4A causes the noise/vibration 2H it will not have any issue. I installed a 3'' kit (not from RC). Light acceleration or hard acceleration the chatter comes and goes at different MPH Im pretty sure its the axles at their limits. Im having a "certified" tech look at it on Monday just (per the lift companys request, even tho I'm a mechanic as well and know I installed it correctly).

Have you also tried in 4H and what is the result? Just want to highlight asking about 4H and whether the same condition also appears, since 4H and 4A behave a bit differently.

 

[Dubsesd]

Have you also tried in 4H and what is the result? Just want to highlight asking about 4H and whether the same condition also appears, since 4H and 4A behave a bit differently.

I will check tonight…. Hopefully I won’t blow my cvs

 

[Oldhippie]

I think it could also be the clutches in the transfer case “fluddering”?? But it does seem like no one actually knows how they engage/slip/lock...

 

[Leesnell91]

4A causes the noise/vibration 2H it will not have any issue. I installed a 3'' kit (not from RC). Light acceleration or hard acceleration the chatter comes and goes at different MPH Im pretty sure its the axles at their limits. Im having a "certified" tech look at it on Monday just (per the lift companys request, even tho I'm a mechanic as well and know I installed it correctly).

Any update on this. I have the 4" zone lift (no diff drop included) and I am getting the same type of vibration/clunking when the front engages. I ordered the Diff drop from Rough country (only a 1/2 inch drop) and it did not fix. Did the tech give you any insight?

 

[Dubsesd]

Any update on this. I have the 4" zone lift (no diff drop included) and I am getting the same type of vibration/clunking when the front engages. I ordered the Diff drop from Rough country (only a 1/2 inch drop) and it did not fix. Did the tech give you any insight?

Not resolved. Zone told me to have it inspected by a authorized certified technician. They need to develop a diff drop. I find it hard to believe no one else has this issue with the kit.

 

[NJNMDoc]

Yea I get a chatter/ vibration. I didn't notice it until after I installed the lift.

Any resolution on this? Are you still getting chatter and vibration? I ask because I’m now getting it as well in Sport. Interestingly this also occurred only post-lift for me too- BUT - I used perch collars so there was no alteration to suspension geometry as had been discussed in this thread.

I thought perhaps it was the 37s input on because it wasn’t doing this after the lift only after the tires did I notice it. Are you running larger tires?

Very interested to know the current statues of your

 

[darinhouston]

I understand (or think I read this, anyway) that some AWDs don't really have a transfer case with mechanical gearing for engaging the second axle but instead use some form of viscosity locking in the transmission to drive power to the desired wheel (or something like that) while in "proper" 4L or 4H, there is mechanical engagement in the transfer case to lock the axles to one another with gears.

 

[HCGxKaLiBeR]

I feel toque steer whenever I accelerate during turns.
Clutch can slip to compensate the rotation differences , but it also wears.

I only use it occasionally. Sometimes I would even go into sports mode, then toggle it back to 2H.

 

[Dubsesd]

Any resolution on this? Are you still getting chatter and vibration? I ask because I’m now getting it as well in Sport. Interestingly this also occurred only post-lift for me too- BUT - I used perch collars so there was no alteration to suspension geometry as had been discussed in this thread.

I thought perhaps it was the 37s input on because it wasn’t doing this after the lift only after the tires did I notice it. Are you running larger tires?

Very interested to know the current statues of your

it’s still there if I pay attention to it. It definitely got better by itself. I haven’t even tried to fix it I’m just rolling with it til someone comes up with a diff drop because that’s what I think the cause is.

 

[NJNMDoc]

it’s still there if I pay attention to it. It definitely got better by itself. I haven’t even tried to fix it I’m just rolling with it til someone comes up with a diff drop because that’s what I think the cause is.

Interesting. Ya FWIW I don’t think it’s the diff drop though. I say that bc my perch lift doesn’t move the geometric configuration of the suspension. The axles are in the same relationship to the diff as OE and yet I have it too. Very minor, but I plan to increase tire pressure a bit and see if there any change in the amount I can notice.

I also wondered if there could be some computer learning going on as well. For example after I went up in tire size I started using normal/2H and being a little less aggressive on the throttle to improve mpg. Previous to that I was rolling hard in sport often.

I didn’t notice the driveline feedback until I switched back to sport randomly one day.

I half wondered if the cpu was adapted to the previous setup with the very lightweight Oe 35s and was now lagging with the added weight.

 

[Sparkherd]

Somewhere, there is a video where a guy disassembles the Advanced Transfer Case, and I can't seem to find it.
The advanced transfer case has a computer-controlled motor which drives a ball ramp system which applies pressure to a clutch pack, transferring torque to the front wheels when the system detects wheelspin on the ass end, or during "handling events". I don't know WTF those are, but I think I've generated a few...
This system has its roots in the F-150 Raptor, and has reportedly given few problems.
The mech in the video said the clutch pack was worn out since the operator drove it in mostly dry weather (no slippage) for 10K miles.
I've used mine a few times in slimy rain conditions; it works great.
I look at it as an "intermediate" option between 2H, dry pavement, no slip conditions, and 4H on completely slippery surfaces.

I stole the following from somewhere here on 6G;

The transfer case has five different operating modes;

• Two Wheel Drive
• Four Wheel Drive - High Range
• Four Wheel Drive - Low Range
• Four Wheel Drive Auto
• Neutral (for recreational towing)

The transfer case is commanded via the mode select switch and the AWD module. The transfer case is electronically shifted via a shift motor mounted on the front of the transfer case housing. The transfer case is filled with lubricating oil which is circulated using a mechanical oil pump. The oil pump is fitted with a strainer to filter any debris.

In four wheel drive mode there is no speed differential between the front and rear axles. This can cause driveline windup when cornering on sealed surfaces.

The Advanced 4x4 with 4A Mode Transfer case is the center of the AWD system. It is a gearbox that attaches to the output of the transmission through a splined input at the transfer case. Torque from the transmission is transferred to the front and rear driveshaft depending on AWD mode.

The transfer case is equipped with an electronically controlled high torque capacity clutch which is located inside the case. This clutch is used to synchronize the speed of the front driveline with the rear driveline during 2WD to 4WD high (4H) or 4WD AUTO (4A) shifts. The clutch also provides torque to the front driveline in all 4WD modes. The transfer case is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.

Two Wheel Drive Operation

In this mode all torque from the transmission is passed through the transfer case to the rear driveshaft which passes through the rear axle and to the wheels.

Four Wheel Drive Auto

In this mode the transfer case system is active all the time and requires no input from the driver. The AWD control system continuously monitors vehicle conditions and automatically applies torque to the front driveshaft. This is done through the use of a multi plate clutch pack inside the transfer case that modulates torque delivery to a chain drive that is connected to the front driveshaft. If any wheel slip is detected on the vehicle or if the vehicle is in a handling event the AWD control system commands the transfer case actuator to apply torque to a ball ramp cam system which then applies an axial force into the clutch pack.

Four Wheel Drive High Range

In this mode the clutch is essentially locked. This would lock the front and rear driveshafts together giving the vehicle maximum traction. It is a similar mode to the ESOF system 4WD high (4H) mode

Four Wheel Drive Low Range

This mode operates the same as 4WD high (4H) but in addition the torque delivered to the transfer case from the transmission passes through a planetary gear set which multiplies the torque by the given ratio. ( In the case of the Advanced 4x4 with 4A Mode transfer case the ratio is 3.06:1 ) While the torque is increased by 3.06 the output speed from the transmission is reduced by the same 3.06 ratio.

 

[Ducati1098]

The mech in the video said the clutch pack was worn out since the operator drove it in mostly dry weather (no slippage) for 10K miles.

I’m going to guess it’s that clown on YouTube called “fordbossme” but I could be mistaken.
However this is a complete myth and unfortunately he is very misinformed with most of his videos. The transfer case and Bronco he was working on had been towed incorrectly and the transfer case damage had nothing to do with normal 4A operation.

Using 4A in completely dry weather does not cause it to wear out any faster than using it in snow or rain. The clutch duty cycle is automatically set to 0 and disengaged by the AWD module for low speeds, low acceleration, tight steering angle and in any instance where driveline binding is present.

The 4A system was specifically designed to be used daily in any type of terrain or weather. There are plenty of Ford vehicles with 150-200k that are only driven in 4A with no issues.

 

[Sparkherd]

I’m going to guess it’s that clown on YouTube called “fordbossme” but I could be mistaken.
However this is a complete myth and unfortunately he is very misinformed with most of his videos. The transfer case and Bronco he was working on had been towed incorrectly and the transfer case damage had nothing to do with normal 4A operation.

Using 4A in completely dry weather does not cause it to wear out any faster than using it in snow or rain. The clutch duty cycle is automatically set to 0 and disengaged by the AWD module for low speeds, low acceleration, tight steering angle and in any instance where driveline binding is present.

The 4A system was specifically designed to be used daily in any type of terrain or weather. There are plenty of Ford vehicles with 150-200k that are only driven in 4A with no issues.

YEAH! That guy!!!
Seems he had a bit of trouble putting that clutch pack together, which is kinda weird for somebody who makes their living as a mechanic.
That's the only vid of his I've seen; I'll take your word for the clown classification.
Good illustration of what's in there tho;

 

[nc-hiker]

You are correct. In 2H, it will never engage anything but the rear wheels.
In 4A, 4 wheel drive is engaged when low traction condition is detected using clutches inside of the transfer case.
I am not sure how well the 4A system works in the Bronco yet, but when I monitor the power distribution screen when in 4A, it shows equal power to all 4 wheels all the time...
I also have a drive train noise when in 4A or 4H, noticeable when accelerating and goes away when you let of the gas/coasting. This is similar to my F-150, so I just assumed it was normal? Maybe its not?

I drive mine in 4A almost exclusively. It's all-wheel-drive. It feels more sure-footed in the rain. I love it. My fuel economy is about 18.5 pretty consistently, which isn't terrible considering I am driving a brick with all terrain tires.

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