4A or 2H? Which is the best?

[BigGreenPony]

So, uh, OP and quite a few of ya'll others on here...WTF are ya'll smoking?!?


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.

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. I 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.

So WTF are these "handling events"?!?
I am pretty sure I cause these on a daily basis...

like many others, I reported better traction and improved steering feel when in 4A. Which seems reasonable.

typically, I’m smoking cigars. Torpedos with a Madura wrapper are the best.

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[Cygnusx1]

I have a Badlands, so I'm missing sport mode. I plan to ForScan this at some point.

highly recommend.

 

[mpeugeot]

Anyone get binding in 4A during slow turns (think backing out of parking spot, pulling in, etc)?

It’s very slight, but you can feel the difference between 2H and 4A in tight parking lot turns. It hasn't hurt anything.

 

[Tofudude]

The 2022 F150 shop manual mentions a heat sensor related to the 4A tcase clutch, which can deactivate the 4A if there is too much heat buildup. I don't know if the Bronco tcase is the same, but if needing to measure heat buildup, that is potential for wear/issues and wasted energy. Maybe not likely but there is that additional complexity.

I wonder why even have 2H on 4A models if there is no difference in terms of performance and wear?

I wouldn't doubt that there is some sort of monitor for it but its still clutch based and will wear with use. I use the 4A mode if I know the trail I am on transitions from dirt and road often or if I am dealing with icy/snowy weather. For most folks using it on the daily its unnecessary and it just adding wear.

 

[FleshTuxedo]

It’s very slight, but you can feel the difference between 2H and 4A in tight parking lot turns. It hasn't hurt anything.

Yeah, I need to get my Bronco checked out. I went to mine after this thread (it was warmed up) and put it in sport, turned out of my driveway and got binding. Then when at the gas station I turned the ignition on and it bucked forward. Something isn't right. I feel like everytime I try to do a GOAT mode (which has been only Sport so far), my Bronco does weird bucks, rolls, etc. Probably not normal?

 

[BigGreenPony]

Yeah, I need to get my Bronco checked out. I went to mine after this thread (it was warmed up) and put it in sport, turned out of my driveway and got binding. Then when at the gas station I turned the ignition on and it bucked forward. Something isn't right. I feel like everytime I try to do a GOAT mode (which has been only Sport so far), my Bronco does weird bucks, rolls, etc. Probably not normal?

Maybe a transfer case or front diff issue? Ford should fix this under warrenty.

 

[indio22]

I wouldn't doubt that there is some sort of monitor for it but its still clutch based and will wear with use. I use the 4A mode if I know the trail I am on transitions from dirt and road often or if I am dealing with icy/snowy weather. For most folks using it on the daily its unnecessary and it just adding wear.

Agreed, the potential seems there for wear with 4A, not to mention additional sensors/mechanism that could have an issue. I like to use history as a guide to how robust a component will be, but we don't have a long service life yet with the Bronco to judge.

If Bronco has similar functioning as the F150 tcase, then per the documentation the system can experience excess energy/heat and require deactivation to protect it. That would probably cause me to not overuse 4A in regular driving:

POWERTRAIN TORQUE PROTECTION: If the system is in 4WD AUTO (4A) and TCCM detects excessive stress or high energy going through the clutch (clutch is slipping excessively while the system is commanding max clutch torque), clutch output will be turned off and message center indicates 4x4 TEMPORARILY DISABLED. When the system had the ability to cool off, 4x4 operation will be automatically restored.

 

[CarmeloS]

I feel the truck is more lively and fun in 2h, so unless its bad weather, I switch right back to it. 4A is alright, but like the rwd nature without the front kicking in because it mistakes me having fun for needing help

 

[timhood]

I came across this issue by accident. I usually switch my truck to 4A for adverse conditions, such as rain, snow, or sleet. This morning I did not turn it off after a big rain and I noticed that the front end felt a lot tighter and the truck handled reasonably better (Not that the handling was terrible before). So, I now have the question, will running my truck permanently in 4A reduce my fuel economy due to all the extra drive strain? Has anyone on this forum tested this?

I'm currently getting 18-19 MPG combined on a 2.3 Badlands Sasquatch manual truck.

You aren't imagining a different driving feel in 4A vs. 2H. It's not significant, though. I stay in 2H unless weather conditions warrant 4H. You'll get a little better MPG in 2H since you aren't driving the front wheels. The nice thing about 4A is that if conditions aren't great, or change during your drive, you don't have to worry about switching to 2H to protect your driveline like you would if you used 4H. Reader's Digest version: 2H until you need 4A. Stay in 4A until you definitely don't need 4A anymore.

 

[Sparkherd]

4A is alright, but like the rwd nature without the front kicking in because it mistakes me having fun for needing help

You Geaux! Boudreaux!!!

 

[BigGreenPony]

Thanks everyone for the comments! Really great information from everyone on the forum. I certainly did not expect this to go to the top of the leader board when I posted this.

 

[FordFamily4Fun]

So if I read this thread correctly (did not get to all of it), 4A in my Bronco is not the same as my AWD only Explorer. Still not sure I understand why. And while they may be different, my Explorer has the same dash setting that shows how much power is going to rear and front axles/wheels. There seems to be a difference because the advanced transfer case in my Bronco can do 4A and 4H/4L while my Explorer can only do AWD? Still not sure why there should be a difference. Is 4A also using 4H in Bronco? I thought that was not advised for dry pavement.

 

[Nc211]

I am not a big fan of AWD, unless if the setup is fixed with a RWD bias. I don’t like torque vectoring and power swirling around the car, makes it hard for me to understand what the car is doing and how to react to it. My last car was fixed 60/40 to the rear, no torque vectoring and all of that stuff, and it was an absolute road machine in all weather conditions. It was a 2014 Mercedes E350 4-Matic sedan. But even with the basic setup, the front diff was going out at 70k miles, even with a fluid change that was not called for at 50k.

I’ve had Toyota (05’ V8 4Runner, 13” Hoghlander), Subaru (99 Outback) and my wife has a MB GLS (2020), all with the swirling AWD setup, and I just don’t like it as a driver. I prefer 2H RWD 95% of the time.

 

[Ducati1098]

So if I read this thread correctly (did not get to all of it), 4A in my Bronco is not the same as my AWD only Explorer. Still not sure I understand why. And while they may be different, my Explorer has the same dash setting that shows how much power is going to rear and front axles/wheels. There seems to be a difference because the advanced transfer case in my Bronco can do 4A and 4H/4L while my Explorer can only do AWD? Still not sure why there should be a difference. Is 4A also using 4H in Bronco? I thought that was not advised for dry pavement.

Not sure what year your explorer is, but if it's a newer platform it works the exact same as the Bronco 4A. The only reason you don't have any other 4wd modes is because it's a completely different transfer case that doesn't have those options.

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