How AWD works (Includes Ford's 4A system)

[Rick Astley]

It's irritating to me how the regulatory environment has driven driver nannies, fuel economy, and cold start emissions to control so many aspects of new cars today. I'm sure well over 99% of car buyers have no clue, and that's why things are the way they are. I'm definitely an outlier. The lack of electronic nannies and fuel economy aids convinced me to buy the Mitsubishi Evolution IX STI even with the old engine tech. The drivetrain is awesome, though.

Sorry, you misspelled a word. Don't like to be a grammar nazi but it makes more sense now, especially considering the drivetrain and vehicle capabilities.

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[Rocketeer Rick]

Thanks for all your info. Can you answer: is there a compelling reason for someone to _not_ leave the vehicle in 4A rather than 2H for _all_ normal use, given you’ve likened this mode to many other vehicles’ AWD systems that are always “on” (waiting for slippage)?

Sure there is - you will burn slightly more fuel in 4A mode. You or I might care, since we might be pushing bigger tires or cluttering up the airflow with racks, winches, lights, etc anyway. But its compelling enough for the OEM to use as a way to get their MPG ratings down. You can also argue that it reduces the duty cycle on the front drive system, but the amount it would be used in normal driving is low. Though it might improve performance in straight-line accelerations.

This is my first post here and I've been wondering if the 4A system in the bronco is the same as the Raptor.

Its fundamentally the same, though probably not the same physical parts. But in all likelihood, it has the same basic configuration and control strategies. But we won't know for sure till we get our hands on them.

 

[wjfawb0 [hacked account]]

Sorry, you misspelled a word. Don't like to be a grammar nazi but it makes more sense now, especially considering the drivetrain and vehicle capabilities.

I looked at EVOs years ago and Focus RS cars more recently. Mitsubishi scared me off and the Focus just wasn't something I could comfortably drive. Transverse engines have never been exciting to me either.

 

[jxosa]

The more reading I do on 4A.its seems the BD does not come in 4A unless you add it as an option..Even my Hyundai has 4A.. what the hell . Not talking 4w drive which is different 4

 

[Rick Astley]

The more reading I do on 4A.its seems the BD does not come in 4A unless you add it as an option..Even my Hyundai has 4A.. what the hell . Not talking 4w drive which is different 4

The article did touch on the variety of "automatic" 4wd engagement methodologies there are out there.

And why your Hyundai is not anything like the Bronco 4A. Check out that section again, they even provide a video to show you some of the trickery that's going on at the ECU to pre-load pressure in the clutch pack

Note that I can't really make out what your last sentence was getting at, sorry if that clarified it and I whiffed at the intent.

 

[jxosa]

The article did touch on the variety of "automatic" 4wd engagement methodologies there are out there.

And why your Hyundai is not anything like the Bronco 4A. Check out that section again, they even provide a video to show you some of the trickery that's going on at the ECU to pre-load pressure in the clutch pack

Note that I can't really make out what your last sentence was getting at, sorry if that clarified it and I whiffed at the intent.

Thanks for the info I believe 4A varies the traction Independently on each wheel as needed. IN 4A. There is no speed limit . I believe 4 wheel drive Lock the wheels in a constant rotation. Thanks for the heads up.. Going to re read the article

 

[Rocketeer Rick]

4A will send power to the secondary axle as is perceived to be needed. But not to each wheel individually. There are some cases like the Bronco Sport Badlands that can power either rear wheel on demand, but it still drives the fronts through an open differential, so all it can do there is use traction control to brake limit the front wheels. It cannot power them individually in the same sense as the rear drive unit can (an open diff will always split available torque 50/50 between the wheels). The only vehicle that would be capable of varying the "traction independently on each wheel as needed" in the literal sense would be an electric car with a motor for each wheel. GM has built a few vehicles that could do that. Of course, we left them on the moon...

That nuance aside, Rick's point that the effective function of the 4A on your Hyundai (and most other CUVs for that matter) and what is in a vehicle like Bronco is quite different is still valid. The base function of a transfer-case 4WD that any Bronco has is - like you point out - significantly different and more capable off road. Yes, the base transfer case will lock the front wheels to the rear wheels when engaged. The locking aspect is why it isn't for road use. But the 4A option adds another layer of functionality to that. It preserves everything the base system can do, but add on the ability use the 4WD "casually" on the road, in assorted conditions. Either way, it is a much more robust system. By that, I mean that it can transfer a lot more torque to the front wheels than your Hyundai can to its rear wheels.

 

[jxosa]

4A will send power to the secondary axle as is perceived to be needed. But not to each wheel individually. There are some cases like the Bronco Sport Badlands that can power either rear wheel on demand, but it still drives the fronts through an open differential, so all it can do there is use traction control to brake limit the front wheels. It cannot power them individually in the same sense as the rear drive unit can (an open diff will always split available torque 50/50 between the wheels). The only vehicle that would be capable of varying the "traction independently on each wheel as needed" in the literal sense would be an electric car with a motor for each wheel. GM has built a few vehicles that could do that. Of course, we left them on the moon...

That nuance aside, Rick's point that the effective function of the 4A on your Hyundai (and most other CUVs for that matter) and what is in a vehicle like Bronco is quite different is still valid. The base function of a transfer-case 4WD that any Bronco has is - like you point out - significantly different and more capable off road. Yes, the base transfer case will lock the front wheels to the rear wheels when engaged. The locking aspect is why it isn't for road use. But the 4A option adds another layer of functionality to that. It preserves everything the base system can do, but add on the ability use the 4WD "casually" on the road, in assorted conditions. Either way, it is a much more robust system. By that, I mean that it can transfer a lot more torque to the front wheels than your Hyundai can to its rear wheels.

THank you..in the old days,my days , you could never drive over 15mph in 4h..can you drive in the rain in higher speeds..I understand what your saying as far as power to front a rear axles but not each wheel indep....never noticed before but now I see..thanks. Has been I my mind and getting alot of different answers. Sounds like you have your shit together(compliment)Again the 4A is an option and should be standard

 

[NCOBX]

AWD is a proactive system, the Bronco does not have AWD. Auto 4WD(ie. Advanced 4wd) is over 20 years old now and is very much a Reactive system.

I really wish we wouldn’t mix terms, if Ford wanted to sell a true AWD system with a lockable center differential they could have. The two systems are entirely different and do not provide the same capability as one another.

 

[jxosa]

AWD is a proactive system, the Bronco does not have AWD. Auto 4WD(ie. Advanced 4wd) is over 20 years old now and is very much a Reactive system.

I really wish we wouldn’t mix terms, if Ford wanted to sell a true AWD system with a lockable center differential they could have. The two systems are entirely different and do not provide the same capability as one another.

Last question... Understand it's not true 4x4 but I was going to upgrade to the advanced 4 by 4 Thinking it was 4A.. Is this a waste of money in your opinion

 

[NCOBX]

Last question... Understand it's not true 4x4 but I was going to upgrade to the advanced 4 by 4 Thinking it was 4A.. Is this a waste of money in your opinion

Up to what you need it for, you can’t use Auto4wd off-road or you will burn up the transfer case from it switching on and off. I suppose it’s useful on the road on ice/snow but your really just revealing a poor set of tires for the conditions - it will get you moving with the wrong tires but won’t help ya stop with the wrong tires.

Fulltime AWD is infinitely more useful on road than Auto4wd. I would consider Auto4wd the system for the unknowledgeable. If you understand the conditions and inputs required then you’re not likely to miss the system.

If your desired setup includes Auto-4wd then by all means don’t avoid it. If your looking at a trim that does not include it then I wouldn’t spend more money to get it.

The only reason not to have a true AWD system with a locking center in this year in time is for the minuscule fuel economy decrease associated with keeping both sets of wheels driven. I feel Ford cheaped out on that.

 

[toymaster]

The more reading I do on 4A.its seems the BD does not come in 4A unless you add it as an option..Even my Hyundai has 4A.. what the hell.

There is a reason for that Padawan. Many Bronco buyers do NOT what the 4A transfer case. I know the off-road world seems like one segment but it is not, it is divided up into many more smaller groups. One of these groups want the simplest system they can get for reliability or because they don't want to waste money on a part/capability they are going to replace anyway. While others, like myself, love the fact we can have an AWD system in such a vehicle while still having a fully locked capability. So, yes it should be an option.

 

[jxosa]

There is a reason for that Padawan. Many Bronco buyer do NOT what the 4A transfer case. I know the off-road world seems like one segment but it is not, it is divided up in to many more smaller groups. One of these groups want the simplest system they can get for reliability or because they don't want to waste money on a part/capability they are going to replace anyway. While others, like myself, love the fact we can have an AWD system in such a vehicle while still having a fully locked capability. So, yes it should be an option.

Thanks for the help with included headliner $300 net upgrade which I did with the dealer no brainer.. Northeast rain and snow and highway driving it's a good thing to have

 

[Rocketeer Rick]

AWD is a proactive system, the Bronco does not have AWD. Auto 4WD(ie. Advanced 4wd) is over 20 years old now and is very much a Reactive system.

I really wish we wouldn’t mix terms, if Ford wanted to sell a true AWD system with a lockable center differential they could have. The two systems are entirely different and do not provide the same capability as one another.

Unfortunately, this is your definition of the terminology - it is not the industry accepted definition (that's just your opinion, man! ). As explained several times in several places, AWD only means that all of the wheels can be powered. That's all. When there are 4 wheels involved, then AWD is the same as 4WD. There is nothing in the SAE definition about pro or reactive functionality. I would love for your definition to be true, because my company's product is a "proper" proactive system. But that isn't the reality of it.

Everything else is just marketing mish-mash. The long running debate of what makes a "proper" 4WD system is just marketing spin. The age old question of what separates AWD from true 4WD is just buzz words and marketing mumbo jumbo. That's all. And everyone's practical definition of what AWD means and what 4WD means is based on that hype and the popular interpretation of it. That's it.

At the end of the day, Ford uses a part-time 4WD system, and offers an extra automatic on-demand function layer as an option. That doesn't make it any less a 4WD. And it does it make it any more an AWD. It just is what it is - 4WD that you don't have to operate yourself if you don't want to. Ford uses the system that they do because it is a lot easier and less expensive to add on-road functionality to a 2-speed t-case if it is in the form of an on-demand clutch then it is to integrate center differential that both locks and works with a high-low gear set. And on top of that, that tiny bit of fuel economy improvement that you right off is gold to manufacturers in today's climate.

With all of that said, I accept the fact that due to bias and buzz, the systems that are typically associated with offroad vehicles are usually called "4WD" and those that are road based are called "AWD". But even then, the method of how the wheels get drive -either full time (proactive) with a center differential like a GX460 or on-demand (reactive) like a CRV, they are both still legitimate claims on the term "AWD".

I also freely acknowledge that there is very much a difference in how these things operate and in the vehicle dynamics as a result. Which is better also depends on who you talk to and what their goals are. I will also point out that modern on-demand systems are, while not fully proactive, do a very good job of predicting when they'll be needed and thus react in advance. That has the net effect of being proactive just the same.

At the end of the day, I agree that this whole field has been confused and mussed up by marketing terms. But let's not confuse it further, OK?

 

[Rick Astley]

Fulltime AWD is infinitely more useful on road than Auto4wd. I would consider Auto4wd the system for the unknowledgeable. If you understand the conditions and inputs required then you’re not likely to miss the system.

Sorry, but this statement had me burst out laughing at my desk.

To observe "the average driver" operating their vehicle on public roadways is to observe an entirely un-skilled, un-knowledgeable population of individuals operating heavy machinery.

The way you worded your statement alllllllllllmost implies that John and Suzie Q Public have any f-ing idea how to alter their driving methodology based on the drivetrain of their vehicle (in dry, perfect weather), let alone in grip-limited situations.

The number of people who have AWD/4WD vehicles and have not one f-ing idea how to drive to maximize the function of the drivetrain their vehicle possesses is appalling and shameful.


Some of my absolute favorite things to observe on public roadways are:

• People with an AWD/4WD vehicle and doing the following:
  • Braking mid-corner
  • Braking at corner exit after over-steering and feeling a miniscule amount of weight transfer back to the inside of the corner
  • Entering corners too cold
  • Constant brake tapping when hitting the landmine of puddles on Seattle roadways most of the year (minor hydroplane situation, usually only for 1 wheel at a time)
• 80-90% of the time driver attention is at most, at MOST 50 feet ahead of their vehicle. You can observe this by watching at what distance people start hitting their brakes when they see a police car or suddenly notice the recovery vehicle lights that was visible 1.5 miles back.
  • Turn signal usage is down to about 30% here in Seattle, so you can't tell if they are even aware 50' out.
  • Those using their turn signal are generally about 20' ahead of their corner/lane change
    • RCW here is 100'
    • https://app.leg.wa.gov/rcw/default.aspx?cite=46.61.305
• STEER WITH THE THROTTLE! For the love of god, you steer with the throttle. Watching people saw away at the wheel or have their will shrink to nothing every time they have to actually use the steering wheel that has sat in front of them every second they have driven a car is hilarious. If your corner entry was that bad, do yourself a favor and steer into the first telephone pole you see instead of making a half dozen course corrections (generally combined with brake tapping with every time they course-correct into the apex due to feeling the weight rotate).
  • Obviously you're turning with the brakes if you're doing a low-grip max speed run such as rally. The person who can't steer with the throttle on public roads should avoid low-grip situations as if their life depends on it, because they sure as hell don't care about anybody else life.

The real kicker, almost 50% of car sales today are AWD/4wd vehicles.... Soooooooo, the theory that only "smart/skilled/educated" drivers choose AWD/4wd is laughable. 4A has a very defined purpose. You also won't be in 4A if you're offroad so no worry about that.

https://gmauthority.com/blog/2020/0...gs were published via,at 50.8 percent in 2020.

The fuel savings is not inconsequential taken fleet-wide, which Ford must do due to CAFE. So if you think that's a cop-out answer, write to your Senator and Congressperson.

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