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Help with 4x4 auto

Discussion in '3rd Gen - 2007 - 2017' started by OldExpy, Apr 27, 2021.

  1. Boostedbus

    Boostedbus Full Access Members

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    It’s great if you find yourself in a counter steer situation and you need those front tires to pull you in the direction of the counter steer....... but you’ve gotta get back in the throttle for that to work.
     
  2. MrSticker

    MrSticker Full Access Members

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    Different model years are engineered and perform differently. I have watched a lot of the Ford videos that splain "how it works". Recent improvements include (what Ford calls) "artificial intelligence" that anticipates the need for power to the front and applies it BEFORE rotational speed differences are sensed.

    My own aha moment was pulling out into traffic on the busy road out of my neighborhood. I was in 2H ... It was wet ... line painted on road for crosswalk ...traffic was coming so I stepped on it so as not to dilly dally & to get out there. Rear wheels spun which doesn't happen in AWD. There are other examples of things that can sneak up on you.

    Plenty of vehicles are full time AWD. There are reasons for that and why they are safer. But still, in theory it's possible to save a few bucks running in 2H. Personal choice.

    https://www.audiusa.com/us/web/en/innovation/quattro.html
     
    Last edited: May 4, 2021 at 6:13 AM
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  3. MrSticker

    MrSticker Full Access Members

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    Here's a question for those that know all the intimate details of how it all works. The actual engineering.

    Let's say you're driving down the road at 50 mph in 2H and you decide to select 4A. It's been explained on this thread that the front wheels are disconnected from drive because vacuum is applied to IWE at front hub. Also purportedly the shaft to that hub isn't turning. So .. you switch. What happens to get the shaft to the wheel to equal the rotation of the wheel so it's an orderly engagement when vacuum is removed? Surely the wheel doesn't connect up with a shaft that's stationary , right? No guesses using common sense, what actually happens?
     
  4. Boostedbus

    Boostedbus Full Access Members

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    Yes that apparently works by sensing rapid increase in torque to the transfer case (hard acceleration). It doesn’t only do it on take off, but even at highway speeds kicking back into passing gear. It’s a great feature I think to not have to unf##k you from a slide with its RSC braking certain wheels to correct you before it senses wheel spin and gives you 4 wheel traction that you need. That’s the kind of technology that I think is great as far as the nanny tech. Not a fan yet of the autonomous vehicles.
     
  5. mnachreiner86

    mnachreiner86 Full Access Members

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    I always thought it was fascinating reading about the development of the initial torque on demand transfer case by Borg Warner in the 80s, what came to be known by Ford as control trac and is the predecessor of what we have today. The story of how they developed the electronics and the multi clutch center diff to replace a gear set is fascinating. Supposedly the early electronics filled the back of a station wagon until it was developed into what came in the first explorers, a package on the transfer case the size of a pack of cigarettes. Apparently the engineers of it tossed the keys to the test vehicle to Ford management and said try it out. Things advanced a long way with the addition of the advance trac system and vsc, and have improved since, but the foundations are still the same. Awesome system.


    Sent from my iPhone using Tapatalk
     
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  6. MrSticker

    MrSticker Full Access Members

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    Me too! I read the first article in Design News back in 1990 or something like that (still available online) and that's why I bought my first Expy. Have owned no other type of vehicle since. In that article (I think) they talked about how they wanted to control it from the drivers seat so they jerry rigged up a fan control switch and to this day (up to my 2014 anyway) that's the same. Reminds me of when I was a computer engineer building a prototype computer over 4th of July weekend (to make schedule) and whatever parts I found laying around in the lab to build the power distribution in the prototype became production and was never changed.

    https://www.designnews.com/automotive/4-wheel-drive-steps-back-future
     
    Last edited: May 4, 2021 at 7:53 AM
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  7. JExpedition07

    JExpedition07 That One Member Supporting Member

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    The hub actuators that lock onto the CV shaft splines are made of a tapered softer metal, when you switch to 4A the hub actuator immediately releases and the splines mesh up. Over time this can cause wear which is why the actuator is sort of sacrificial. My actuators were totally shot on my last truck but the CV axle splines had virtually no wear on them. The actuator is sort of sacrificial and they do indeed just release and lock up quick. It’s good to shift to and from at lower speeds because of this, yes you can shift up to 50 MPH but it’s a lot of extra wear on that softer metal part.
     
  8. 07navi

    07navi Full Access Members

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    The shafts from the diff ARE turning, when you select 4 auto it puts the driveshaft, diff, and axles into motion and the IWE locks it all together. If that didn't happen you could grind me a pound......like the saying goes. There goes your azzes with opinions theory.:emotions34:

    This is why it makes no sense to wear those parts out and sabotage your MPG's in normal driving conditions. Tricky engineering but not really that useful. I think they did away with it on later models.......don't quote me on it.
     
    Last edited: May 4, 2021 at 5:53 PM
  9. Thunderbirdsport

    Thunderbirdsport Full Access Members

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    Rather than all the speculation as to how, why, and what will happen (which we all *should* know will happen and that is not a whole hell of a lot of anything), how about those who claim the world will split in half if someone were to drive around in 4A post their actual combined mileage while in nothing BUT 2H, while someone who uses ONLY 4A posts their mileage?

    I get that there *may* be increased wear on a few things, but overall.....it's not instant death of humanity. There's been literally millions of Ford SUVs in the last 20 years with some sort of AWD system, and while the methods of that AWD, or in this exact instance as pertaining to Expys, 4A (which in this case is fundamentally identical), it stands to reason that if it was that harmful, then Ford, themselves would state clearly and equivocally to NOT do it unless on slick shit. Am I wrong?

    I know there's a few experts here (tongue firmly in cheek) who will argue that mileage goes down drastically, or that axles will break in a lot less miles, etc...and while they not wrong, nor are they correct, fully.

    If I lost half an MPG due to running solely in 4A rather than just 2H, or 4H when needed, to me, that's a non-issue. If the badge on the back said Prius instead of Expedition.... ;)

    As for wear and tear on actuators....they're a made to fail part. They are meant to be replaceable.
     
  10. 2015-EL-Limited

    2015-EL-Limited Active Member

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    We got our '15 Ltd 4WD 6 months ago with 110K. Noticed also that the truck does not like to downshift until RPMs get below 1,100 (approx.) resulting in lugging for a bit followed by an abrupt downshift. Now at the first sign of lugging, I downshift with the rocker switch on the shift lever, bumping the RPMs back up above 1,500 with a smooth transition and all's fine.
     

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