How 4A mode works?

[Buyer2021]

If only Ford were as good at educating their customers! I’m actually going to have to say they’re more than blasé and that they’re downright apathetic about the torque on demand transfer case.

While the advertising / customer education side of Ford seems to be lacking (OK, sorely lacking) in this regard, at least the engineering folks seem to remain interested and involved / evolving.

I note and don't argue with your points about IWE, mileage, and the potential role of CAFE-related incentives or lack thereof.

I, for one, am glad to have the TOD with 4A, even without IWE. Yeah, I may well suffer a ~1 mpg hit for every 2H mile, and yeah, the majority of my miles are in 2H. But it seems that IWE (at least the earlier vacuum version, not sure if there's a track record for E-IWE) is a potential point of reliability issues and I'm glad to not have to mess with actuating 'good-ole-simple' manual hubs. Maybe some other manufacturer has a better idea for automated hub freewheeling, but I'm sure that's not gonna incite me to abandon my F150.

So all-and-all I'm OK paying a bit to churn that differential fluid. Other opinions may differ of course.

Compromises, always compromises .....

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[Pedaldude]

It’s also nice to see that they are still improving the TOD TC and TCCM. The first generation one on my Lincoln combined with clutch pack LSDs front and rear is amazing in the wet, I would love to see how it is in the snow but I don’t exactly live in the best place for that. My Lincoln gets 12MPG city but costs less to operate than the shitbox 35MPG economy car it replaced. The added feeling of security can’t be measured!

The manufacturers are well past the point of diminishing returns on fuel economy vs. reliability.

While most people are focused on the MPG number, because that’s what’s being pushed; the one that they should pay attention to is lifecycle cost. Who gives a shit if you save one or two miles per gallon if it’s at the cost of grenading the engine? Auto start/stop, turbos, cylinder deactivation and many other things aren’t exactly good for engine longevity.

An IWE failure is relatively benign but say after 50K miles a repair is needed. You saved a thousand dollars in gas by getting better mileage. What broke though and what are the costs? It doesn’t take much to erase any savings. Even if it’s just a few dollars for a part, if it’s a five hour job in the books...

The most messed up part is that you are probably not saving any fossil fuels either because the amount of energy needed for a new part or entire truck is astounding. If a truck goes to the scrap yard a few years earlier and tens of thousands of miles less than its predecessor: you haven’t saved anything, it’s actually costing way more in the long run in energy from fossil fuel and other sources. Even if the foam from the seats is soy based it costs diesel fuel to run the tractors at the farm.

Those stupid reusable grocery bags are the perfect example. They use 100X the amount of fossil fuel but maybe get used an average of 20X before they have been expended. Not only that, but when you get food poisoning from raw chicken juice, what’s the cost of that? Environmental groups are actually fighting against some of the new feel good measures because they are a huge step backward. I feel many of these automotive ‘improvements’ are much the same.

Even if 4A costs a little more a mile. How much does it cost to replace a wheel/tire after fish tailing into a curb or tagging a fence post with the RADAR equipped rear taillight? The 4A TC is one of the few improvements where added complexity isn’t at the cost of reliability. Most of these transfer cases are outlasting the vehicles that they were in. It really should be the standard equipment for all the 4X4 trucks and if CAFE numbers are keeping it from happening, it’s a shame.

Happy New Year everyone, I’m thankful that this is a great place where we can share and discuss different opinions like adults!

 

[Polo08816]

It’s also nice to see that they are still improving the TOD TC and TCCM. The first generation one on my Lincoln combined with clutch pack LSDs front and rear is amazing in the wet, I would love to see how it is in the snow but I don’t exactly live in the best place for that. My Lincoln gets 12MPG city but costs less to operate than the shitbox 35MPG economy car it replaced. The added feeling of security can’t be measured!

The manufacturers are well past the point of diminishing returns on fuel economy vs. reliability.

While most people are focused on the MPG number, because that’s what’s being pushed; the one that they should pay attention to is lifecycle cost. Who gives a shit if you save one or two miles per gallon if it’s at the cost of grenading the engine? Auto start/stop, turbos, cylinder deactivation and many other things aren’t exactly good for engine longevity.

An IWE failure is relatively benign but say after 50K miles a repair is needed. You saved a thousand dollars in gas by getting better mileage. What broke though and what are the costs? It doesn’t take much to erase any savings. Even if it’s just a few dollars for a part, if it’s a five hour job in the books...

The most messed up part is that you are probably not saving any fossil fuels either because the amount of energy needed for a new part or entire truck is astounding. If a truck goes to the scrap yard a few years earlier and tens of thousands of miles less than its predecessor: you haven’t saved anything, it’s actually costing way more in the long run in energy from fossil fuel and other sources. Even if the foam from the seats is soy based it costs diesel fuel to run the tractors at the farm.

Those stupid reusable grocery bags are the perfect example. They use 100X the amount of fossil fuel but maybe get used an average of 20X before they have been expended. Not only that, but when you get food poisoning from raw chicken juice, what’s the cost of that? Environmental groups are actually fighting against some of the new feel good measures because they are a huge step backward. I feel many of these automotive ‘improvements’ are much the same.

Even if 4A costs a little more a mile. How much does it cost to replace a wheel/tire after fish tailing into a curb or tagging a fence post with the RADAR equipped rear taillight? The 4A TC is one of the few improvements where added complexity isn’t at the cost of reliability. Most of these transfer cases are outlasting the vehicles that they were in. It really should be the standard equipment for all the 4X4 trucks and if CAFE numbers are keeping it from happening, it’s a shame.

Happy New Year everyone, I’m thankful that this is a great place where we can share and discuss different opinions like adults!

My GF experienced this on her 2004/2005 Honda Civic Hybrid MT. The hybrid battery failed and causes a CEL. In Maryland, a CEL means your car does not pass inspection. The replacement cost for the hybrid battery was anywhere between $2-4k which, in my opinion, erased much of the fuel savings cost.

 

[air2mag]

I agree with you guys on the 4A. It’s part of the rest I moved up models. My wife pulls her horse trailer with the truck. I tell her to use tow haul mode if the road is dry. If it’s not use slippery mode. When in doubt slippery it is. Towing mileage is bad no matter the mode so I don’t factor that in. We haven’t towed enough with the new truck yet to see where the mileage falls. I would venture to say slippery and tow haul will be close to the same.

 

[powerboatr]

mine stays in 4A almost all the time
however long road drives it goes back to 2H..if road conditions warrant
although i cant say if i have seen any MPG change with 2H versus 4A
4A does plant some pwr up front if you get on the throttle.. that might be why sport mode defaults to 4A mode

 

[bwwF150]

I should look at the manual ... any speed limitations on using 4A? 85mph ok?

 

[Buyer2021]

any speed limitations on using 4A?

None stated IIRC.

 

[Snakebitten]

I have many thousands of miles in 4A and never even a hint of an issue related. But full disclosure:

I haven't had a high mileage truck to vouch for such use.
I haven't and wouldn't use it for heavy towing.
And it would be odd circumstances that I would be on dry pavement at Texas interstate speeds (85mph) in 4A, although I absolutely have switched to 4A on Interstate 10 in sloppy weather.

In all these years I don't remember much documented about 4A failures. Although IWE and/or front differentials are far from immune to issues. Just not 4A as a contributing source.
I think it's fairly proven at this point.

 

[Tomatoboy]

I should look at the manual ... any speed limitations on using 4A? 85mph ok?

Negative. The manual states no speed limitation for use of 4A. The system is capable of disengaging the clutch pack on its own, based on its own thermal strategy and the various inputs it monitors and manages it by itself, if it needsto disengage. Anecdotally, my vehicle continues to apply power to the front wheels at that speed during heavy throttle input. 4A has no speed or surface type limitations, which makes sense, as it’s effectively just an AWD mode.

 

[Pedaldude]

I should look at the manual ... any speed limitations on using 4A? 85mph ok?

My 2001 Navigator only has 4A as an option for highway use even though the first generation torque on demand transfer case it’s equipped with is capable of 2H.

Before I bought it from the original owner, I did extensive research into both the 5.4 32V Intech engine and its powertrain. Reading about the development of the 4A TC, I read several testimonials from Ford and Borg Warner employees that the pre-production mules were worn out long before the transfer cases were during extreme use.

The real limitation on the 4A mode on the TOD TC is slow off-road applications, especially sand. Where the transfer case will overheat.

Because of this limitation the Raptor and some Tremor trucks are equipped with the Hi-lock TC that has a dog clutch in addition to the friction clutch pack to turn the TOD TC into a conventional part-time TC for heavy off-road use.

The regular 4A transfer case also has 4H and 4L, which at least in the first generation cases; locks the friction clutch pack together the best it can in both high and low range. This works fine if you are carrying enough momentum off-road but if you are rock crawling or driving like you want to get stuck in deep gravel or sand, then the clutch pack can still slip.

Ford saw fit to have the first generation Navigator only in 4A for all highway and city driving for the entire life of the vehicle and there’s still some available used with over a quarter million miles.

As from my earlier post, if you have 4A, just do as Ron Popeil says.

 

[Nomis]

All I know for sure is it doesn't behave like 4A in my previous truck, a GMC. If I punched it on icy roads in my GMC all tires would 100% spin and pull me straight. Picture I go to turn and start sliding, punch it to correct the slide. With this truck they seem to alternate and do weird things and slide me side to side.

It also only has 1300 km on it so I don't know, but it definitely behaves differently. Slower to engage or something. Traction control is also quite different between the brands though. I usually turn it off in the winter unless im on the highway.

4A was a deciding factor for me choosing a Lariat because I pretty much always ran it when i need more traction, be it on the highway or offroad. Only in really demanding situations would I use 4H.

Now it seems I have less control on say snowy roads at low speed with this ford 4A, so I use 4H instead. Still 4A on highway though. This is all winter driving as I just got the truck a couple weeks ago.


Im not a set it and forget it guy though. I run 2wd most of the time unless it's icy or I'm off-roading.

 

[3Ranger11]

When did Ford ditch the IWE? They just ditched the vacuum system and went electronic in the 21’s.

 

[waphilips]

FWIW, following in italics is a verbatim excerpt clipped from the the Ford Workshop Manual (TCCM = Transfer Case Control Module):
_____________________________________

307-07A Four-Wheel Drive Systems
2022 F-150
Description and Operation Procedure
revision date: 03/24/2022

Four-Wheel Drive Systems - Vehicles With: 2-Speed Torque On Demand Transfer Case - System Operation and Component Description
......

In 4WD AUTO (4A), the TCCM continuously monitors conditions and driver input to send torque automatically to the front driveline by controlling the transfer case clutch, providing 4WD capability. The TCCM sends a duty cycle command to the transfer case clutch coil as a torque request based on combination of preemptive and wheel slip response algorithm. Preemptive response is based on steering wheel angle, vehicle speed, throttle positions and available powertrain torque. Wheel slip response is based on monitoring the average front and rear wheel speeds.

When 4WD is no longer needed (during cruising or steady state driving) system defaults back to RWD (rear wheel drive) mode by setting the duty cycle output to 0.

TCCM increases the duty cycle to prevent or control slip under any of the following conditions:

• Slip is detected.
• Heavy acceleration (throttle position).
• Straight-ahead steering wheel angle.

TCCM decreases the duty cycle to prevent or reduce vehicle bind under any of the following conditions:

• Low speed.
• Low acceleration (throttle position).
• Tight turn steering wheel angle.

The TCCM has a thermal hardware protection strategy which monitors the amount of energy going through the clutch. This strategy has 2 levels of protections:

AUTOLOCK: If the system is in 4WD 4H [***] and TCCM detects driving conditions that require greater 4WD performance, the TCCM temporarily turns on 4WD (4H) from 4WD AUTO (4A) after detecting driving condition and informs the customer via the message center indicating 4X4 TEMPORARILY LOCKED. The 4WD system automatically returns to 4WD AUTO (4A) after the system no longer detects these driving conditions and informs the customer via the message center indicating 4X4 RESTORED.

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.

NOTE: The 4x4 Temporarily Disabled message can be dismissed by the customer however it's advisable to let the TCCM clear the message itself, which indicates that the 4x4 system has resumed normal operation.
.....
_______________________________

[***] NOTE - I believe that the term "4WD 4H" used here is a typo in the WSM text and should be "4WD 4A".

I suggest that the pictorial power distribution display simply isn't programmed with the sophistication required to reflect the sophistication of the actual moment-to-moment driveline behavior / status when in 4A mode. Yeah, that's a bit cheesy (and maybe a bit lazy on Ford's part, it would seem that the duty cycle commands from the TCCM could be used for the purpose of altering that display image to reflect what's really going on) but that display has nothing to do with the actual functioning of the system. On the other hand that might be intentional to prevent folks from freaking out when they see how little time is actually spent with power directed to the front wheels when in 4A mode ().

awesome post -- thx for the info

 

[gadiedrick]

Manufacturers don't go into detail because 99%+ buyers simply don't care. I've overheard conversations already of people that bought/leased vehicles and didn't realize how something worked until after they signed the paperwork. I'm sure there are a vast number of drivers that couldn't even tell you if their car is FWD, RWD, AWD, or 4WD. If they did know, and it was an AWD vehicle, they probably have no idea how the AWD system works or what the limitations are.

Help me out here ....... I don't think that the 4A option was available when we took delivery of our '21 F150 Powerboost in FEB '21. If it was. I've not found it listed on our window sticker or in the operator's manual, which we had to purchase on line 'cause Ford did not include the manual in our vehicle. That 4A option sounds good & we do have AWD in our '21 Pacifica which helps winter drive'n in the midwest. Regardless we're not about to trade our PB if we don't have 4A.

 

[Tomatoboy]

Help me out here ....... I don't think that the 4A option was available when we took delivery of our '21 F150 Powerboost in FEB '21. If it was. I've not found it listed on our window sticker or in the operator's manual, which we had to purchase on line 'cause Ford did not include the manual in our vehicle. That 4A option sounds good & we do have AWD in our '21 Pacifica which helps winter drive'n in the midwest. Regardless we're not about to trade our PB if we don't have 4A.

It isn't a stand-alone option. It’s automatically included on trims from Lariat on up (excluding Raptor*) unless you get the snowplow package** if you have a 4x4. Your vehicle would be labeled having the “Two-Speed Automatic Four-Wheel Drive System with Neutral Towing Capability (4x4 Only)” rather than “Electronic-Shift-On-Fly (ESOF)“ with Neutral Towing Capability (4x4 Only) you get on the XL, XLT, and Tremor (unless you opt for the optional Hi-Lock on the Tremor). Ford only gives you 4A based on trim selection.

*Raptor gets the Hi-Lock by default which has both 4A and a locking clutch.
**if you get the 5.0 and opt for the snowplow package you still get the ESOF case not the 4A one, apparently for duty cycle reasons.

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