4A issues. ford says this is normal?

[tourproto]

FWIW ... bought my Badlands new and yes I can tell a difference in how it steers in 4A vs 2H but not by much. I would not use 4A unless you are on wet, snowy, or icy conditions. 4A uses a clutch to engage when needed but I suspect there is a little drag in it even when disengaged when 4A is on ... good luck!

In my opinion: 4A provides zero advantage over 2H in normal driving conditions and also contributes to internal transfer case clutch pack wear. I would only use it on high speed dirt road driving, heavy rains or intermittent icy conditions.

MY OPINION.

I guess we can all get back together in 2040 and see who still has their Bronco and who has had to have their transmission replaced due to "inappropriate usage of 4A on dry pavement". I intend to keep my Bronco for a long time (my prior vehicle ownership is 18 years and 20 years)

I will be using 4A all the time unless I am in 4H or 4L. I won't be using 2H. I guess time will determine who is right with regard to 4A usage as it pertains to reliability.

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[Ducati1098]

Question: The literature says when slip or potential slip is detected it engages 4wd. How does it know when the slip or potential slip condition is over and it should disengage?

Logic built into the AWD module using other various sensors for information.

 

[thegoatman]

The power distribution screen on the f150 shows exactly when the clutches are being engaged and the amount of engagement.

going straight, under 45-50mph, the front wheels are engaged. Over 60 cruising straight down the highway, there’s no engagement unless an event causes it to be applied like hammering on the gas

 

[Malicar]

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.

This is the juicy info I needed. Thank you! Clear as day how the system works now.

 

[Malicar]

I'm genuinely curious what you thought "electronic" meant in this context. "Electronic" here is used no differently than it is for an electronic automatic transmission (ubiquitous nowadays, to the point where it's not even mentioned, it's just assumed) or an electronic LSD (on an increasing number of performance cars). Just a layer of control (logic and actuators) over a mechanical system. Hopefully (and this appears to be the point of contention in this thread) with enough intelligence in the programming and robustness in the hardware to add benefit without causing additional wear.

The eLSD is particularly interesting to me, as this seems to be similar to what we're talking about. Basically a clutch-based rear locker, engaged selectively, to give performance like a LSD. You could argue that if they did it wrong (too much engagement for too long in the wrong conditions) they'd stress the LSD clutch too much and burn it out. And yet such cars don't (to my knowledge) enable to you to turn it off. Furthermore, the dashboard displays on some cars seem to indicate that it's always at least partially engaged.

4A is obviously different than an eLSD, it's engaging a clutch in the transfer case to selectively send power to the front wheels rather than selectively "locking" the rear wheels together. But on a broader level, I don't see why a well designed 4A system couldn't be controlled and/or built robustly enough to to withstand the stresses of running full time on dry pavement just like the eLSDs are.

Having said all of the above, I'm not a mechanical engineer, happy to be corrected. I don't run 4A all the time in my Bronco, I just don't see the need most of the time. More importantly (to me), I have two other cars that DO have clutches distributing power to various wheels that ARE constantly slipping (one of which can overheat when pushed hard on the track), so I hope this is a (mostly) solved problem.

https://www.motortrend.com/how-to/combining-electronic-controls-and-automatic-transmissions/

https://www.corvetteforum.com/forums/ask-tadge/4030900-answered-how-to-decipher-elsd-display.html

https://www.grcorollaforum.com/threads/gr-four-awd-system-discussion.321/

Electronic I figured electronically controlled or actuated. I've had a few vehicles that have had an all mechanical AWD system, where there is a clutch pack or viscous coupling that does all the work.

Ford calls the front diff a drive unit, so I figured something sneaky was going on the inside out of ignorance

 

[Malicar]

I will be using 4A all the time unless I am in 4H or 4L. I won't be using 2H. I guess time will determine who is right with regard to 4A usage as it pertains to reliability.

I mean, at the very least it will need new clutch packs sooner, just due to more usage.

I've never thought about having to do a clutch swap on my transfer case before..

 

[thegoatman]

Electronic I figured electronically controlled or actuated. I've had a few vehicles that have had an all mechanical AWD system, where there is a clutch pack or viscous coupling that does all the work.

Ford calls the front diff a drive unit, so I figured something sneaky was going on the inside out of ignorance

I believe there was an explorer at one point that used a Torsen in the center diff

 

[BigMeatsBronco]

The clutch is controlled electronically and It’s all done inside the transfer case.

Transfer Case
OPERATING PRINCIPLE

The transfer case delivers engine torque to the rear wheels and to the front wheels, when requested. The transfer case is mounted on the rear of the transmission assembly. The transfer case has an integrated low range gear reduction using the planetary gear set.

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.

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



It just locks the clutch.

That's not necessarily correct, there's no way in hell the clutch pack could withstand the forces generated in low range.
This video shows a splined connection in 4H...the center splined collar slides in between the two shafts when the motor is driven all the way to the farthest point.

 

[Ducati1098]

That's not necessarily correct, there's no way in hell the clutch pack could withstand the forces generated in low range.
This video shows a splined connection in 4H...the center splined collar slides in between the two shafts when the motor is driven all the way to the farthest point.

Right, it’s essentially locking the clutch like the information says.
I didn’t post anything about low gear because nobody ask about that, but here is what it says for that:

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.

Also for anyone else that watches that video, please don’t listen to anything that clown “fordbossme” has to say about 4A transfer case operation. He’s a complete idiot and has absolutely no idea what he’s talking about. Although this is a good look at the inner workings of the tcase.

 

[BigMeatsBronco]

Right, it’s essentially locking the clutch like the information says.
I didn’t post anything about low gear because nobody ask about that, but here is what it says for that:

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.

Also for anyone else that watches that video, please don’t listen to anything that clown “fordbossme” has to say about 4A transfer case operation. He’s a complete idiot and has absolutely no idea what he’s talking about. Although this is a good look at the inner workings of the tcase.

Agreed, in his defense, he does mention at the end that it was most likely flat towing that cause the damage. but either way, I'm not taking his advice.

 

[tourproto]

I mean, at the very least it will need new clutch packs sooner, just due to more usage.

I've never thought about having to do a clutch swap on my transfer case before..

I guess time will tell if that will be needed or not. Ran our Explorer in 4A for over 15 years and never had a problem...

 

[KABQ]

In terms of operation (not usage, that's been covered quite enough) my 4A delivers equal power distribution to the front and rear wheels at all times, but has no binding like it would in 4H. Since it is supposed to be an on-demand system, is it normal for it to operate this way?

 

[V1Rotate]

In terms of operation (not usage, that's been covered quite enough) my 4A delivers equal power distribution to the front and rear wheels at all times, but has no binding like it would in 4H. Since it is supposed to be an on-demand system, is it normal for it to operate this way?

Mine does not. Its RWD only until I get on the gas a little bit harder. It also goes RWD only in sharp turns

 

[twinturbo4vGT]

UPDATE: Ford found the transfer case was indeed bad stating it was stuck in 4H ALL the time and are replacing it under warranty. Multiple techs took the truck for a drive and immediately knew something was wrong.

 

[twinturbo4vGT]

In terms of operation (not usage, that's been covered quite enough) my 4A delivers equal power distribution to the front and rear wheels at all times, but has no binding like it would in 4H. Since it is supposed to be an on-demand system, is it normal for it to operate this way?

No it's not supposed to do that! Have it checked immediately!

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